>> reporter: in the staudte family, they're bizarrely dying off. one after another. a husband, dead of "natural causes." >> there was no autopsy, no testing. he was cremated, his ashes were scattered at a lake, that was it. >> reporter: a son, dead from seizures. >> and i'm like, oh, my god, this mother must be devastated. she lost her husband, now she loses her, her son? >> reporter: a daughter, hanging on to life in the e.r., with "flu-like symptoms." >> it's bad. she was as close to death as you could get. >> reporter: and a mother and wife, a devout church organist left to shoulder the burden. >> either this is a terribly unlucky family, or something fishy happened here. >> reporter: but just how fishy?

out in a stunning interrogation. >> dear god. >> reporter: tonight, piecing together the secrets in a highly unusual family, the tell-all diary, their bedside reading. >> we had a book on poisonous plants. >> reporter: their garage, always prepared for an emergency. >> who has antifreeze in the summertime? >> reporter: and a very strange way of expressing sympathy. >> i didn't want another one to die in the house. >> why is that? >> because houses are nasty after somebody's died in it. >> reporter: so who's left in the family, if they can survive long enough? >> did you think somebody else was going to be next? >> reporter: talking on camera for the very first time only to "20/20." the daughter who did live to tell. >> i consider them as killers -- who hate me. >> reporter: what's wrong with these people? >> what were you thinking at that point? >> oh, god. another one.

>> reporter: a family plot. >> good evening, i'm david muir. >> and i'm elizabeth vargas. tonight, we're taking you inside an investigation that "20/20" has been working on for more than two years. >> and right here tonight, the clue in a secret diary that would tie everything together. an ominous line that say, only the quiet ones will be left. >> we'll be tweeting throughout, so weigh in as it unfolds. here's debra roberts. >> reporter: at the foothills of the ozarks, sits branson, missouri, the las vegas of the midwest. drive 45 miles north on old route 66 and you're in springfield, a tranquil college town where the buckle of the bible belt meets beer joints. here on page street, a modest 900-square-foot home, diane staudte and her husband mark embody that unlikely mix of holy water and fire water.

she's the church organist down at redeemer lutheran. ♪ he's the lead singer and guitarist of a local blues band messing with destiny. you'll get the irony of that later. together the couple, former college sweethearts, are raising four kids in that small house. six people, three small bedrooms, one bath. tight quarters for what looks like a tight family. did you get any sense of what their relationship was like? >> as far as i knew, mark's wife was great. >> reporter: charles alexander is mark's close buddy and the drummer in the band. >> he was always happy with the kids, he was always happy with his wife. he loved them. he loved his family. and it was just a great family. >> reporter:

great for everyone. see, diane isn't just praying in church. she's paying the bills at home. okay, mark picks up an occasional shift bartending. but diane, a nurse is the breadwinner. >> she seemed to be stable and ended up supporting him. he was the house husband, stayed at home with the children. >> reporter: and if mark was a laid-back mr. mom, the actual lady of the house was civil, if a bit standoffish. was diane friendly, warm? >> you know, she was friendly to the point that, "i can tolerate you being in my driveway." >> reporter: as the years wear on, life just keeps heaping more weight on diane's slight shoulders. supporting her family in that cramped house and coping with some heavy challenges. fourth grader, brianna, has a learning disability. son shaun has autism and oldest daughter sarah, a college grad, is still at home, with no job and a mountain of student debt. but inside that page street pressure cooker, diane's beloved child is blossoming -- 22-year-old rachel, a star student. this is the relationship that would forge the whole family's fate. >> s c

time rachel had an accomplishment. when you look at it from the outside in, you think, "that's a really close mother-daughter relationship. and isn't that great?" >> reporter: ron davis with abc affiliate kspr-tv took us to the staudte home. and what was it about rachel that drew her mom to her so intensely, do you think? >> by all indications, rachel is an exceptional human being. very smart, very talented, artistic. >> reporter: on facebook, diane raves about her beloved rachel, her art, her academics. but a nary mention for her husband mark, who in april of 2012, is finally having his moment in the spotlight. >> we had a good band. we were literally taking off. >> reporter: he's flying high. messing with destiny is booking semi-regular gigs in branson, joining the aretha franklin impersonators to get marquee

it's also mark's birthday weekend. these are pictures from rehearsal that night, where charles notices that mark isn't quite himself. what did you think was going on with him? >> he was just so out of whack. and it wasn't like he was drunk or anything. he was just out of whack. he wasn't with us. >> reporter: then the next day, more odd behavior. >> he just showed up at my door one day, on a saturday. and i said, "mark." and he goes, "oh, i'm here to celebrate my birthday, charles!" only one thing struck me so out of place, his skin color. >> reporter: what did it look like? >> yellow. his skin was actually a yellowish color. >> reporter: so something was wrong with him. >> something was wrong with him. >> reporter: he's right. on easter sunday, diane comes back from church and finds her husband dead in bed. >> i was devastated. i was devastated. >> reporter: did you have any inkling that anything was wrong? did you get any clue that mark's health might have been bad? i mean --

>> reporter: yet diane tells authorities her husband's been sick and refused to see a doctor. there's a curious ring of blood around mark's mouth, but it's not enough to alarm the medical examiner, who rules the death "due to natural causes." >> it was a bit of a shock, but i thought, "well, you know, he doesn't really exercise. he doesn't really cook, so probably not real healthy eating habits." >> there was no autopsy, there was no testing, he was cremated, his ashes were scattered at a lake, that was it. >> reporter: diane organizes a memorial service at redeemer lutheran church. >> it was, it was sad. it was a sad event. the wife wanted us to do a song in his honor. so we played the song. >> reporter: mark's favorite song, "darkest hour." this is their audio recording from that day. ♪ >> reporter: as the family copes

there's a small consolation, a $20,000 life insurance payout, enough for diane to move the family to a new neighborhood and a larger home. >> they moved into this house, right here. >> reporter: oh, big difference. >> it definitely is. it's a step up from where they were. >> reporter: when we come back, the staudtes may have moved on up, but their bad fortunes are just beginning. >> the coroner's van was in their driveway. >> reporter: because whatever afflicted mark seems to run in the family. >> i said it was impossible. i was floored. >> reporter: and eventually police will suggest a different diagnosis. >> my husband died last year of a heart attack. >> did he? >> reporter: stay with us. i was energetic. then the chronic, widespread pain drained my energy. my doctor said movinre helps ease fibromyalgia pain. he also prescribed lyrica. fibromyalgia is thought to be the result of overactive nerves. lyrica is believed to calm these nerves.

relieve fibromyalgia pain and improve function, so i feel better. lyrica may cause serious allergic reactions or suicidal thoughts or actions. tell your doctor right away if you have these, new or worsening depression, or unusual changes in mood or behavior. or swelling, trouble breathing, rash, hives, blisters, muscle pain with fever, tired feeling, or blurry vision. common side effects are dizziness, sleepiness, weight gain and swelling of hands, legs and feet. don't drink alcohol while taking lyrica. don't drive or use machinery until you know how lyrica affects you. those who have had a drug or alcohol problem may be more likely to misuse lyrica. with less pain, i can be more active. ask your doctor about lyrica. ...another anti-wrinkle cream in no hurry to make anything happen. neutrogena® rapid wrinkle repair works... ...in one week. with the... fastest retinol formula available. it's clinically proven to work on fine lines and... ...even deep wrinkles.

that definitely works!" rapid wrinkle repair. and for dark spots, rapid tone repair. neutrogena®. "see what's possible." introducing oikos crunch. greek nonfat yogurt with delicious crunchy toppings like chocolate and peanut butter chips. crunched it! new oikos crunch. be unstoppable. (p...that, you haveit, wait! yoto rinse it first like... that's baked- on fredo. (p...tbaked-on? it'st, wait! yonever gonna work. like... dish issues? cascade platinum... powers... through... your toughest stuck-on food. let your dishwasher be the dishwasher. see? told you it would work.od. cascade. late friday and early saturday... and get tek-gear for the whole family under $10... tees under $10... and shorts and capris for the whole family under $20! plus, take an extra 15 percent or 20 percent off! you'll get kohl's cash too! kohl's. listerine® kills 99% of bad breath germs.

sh mouth. what's it like to not feel 100% fresh? we don't know. we swish listerine®. as do listerine® users. the very people we studied in the study of bold. people who are statistically more likely to stand up to a bully. do a yoga handstand. and be in a magician's act. listerine® kills 99% of bad breath germs so you can feel 100% in life. bring out the bold™. flea bites can mean misery for your cat. advantage®i monthly topical kills fleas through contact. fleas do not have to bite your cat to die. advantage® ii. fight the misery of biting fleas.

"20/20" continues, with a family plot. >> reporter: at redeemer lutheran church, pastor jeff sippy tends his flock with fervor and passion. >> we are jumping for jesus. >> reporter: and in the summer of 2012, devout organist diane staudte has good reason to lean on the pastor's sermons for strength. >> mary arose and went with haste in the hill country. so you can see a woman with a mission.

>> reporter: her husband mark has recently died. and she's just moved with her four kids to this friendly street, hoping to put that sadness behind them. rhonda anderson, a church secretary, lives across the street. did you see them going and coming? >> one day the garage door was open and i thought, i'm going to go over there and say, "hi." and just as i got over there, it was really like they looked at me and closed the garage door, really, because i could still seem them standing there. so i don't think they wanted to talk to anybody. >> reporter: rhonda doesn't take it personally, leaving her private neighbors to themselves, until weeks later, one sunday in september she looks out the window and is shocked by what she sees. >> the coroner's van was in their driveway. a policeman said there was a death in the home. i was blown away. >> reporter: once again, death has knocked on the staudte's door. the firstborn child, shaun, gone at 26. diane tells police he had

flu-like symptoms for three weeks. >> she reported she checked on him at about 6:30 in the morning, went to church, and then when she came back from church, found him not in bed anymore but on the floor without a pulse. >> reporter: she explains that her son had a history of seizures, and though like his dad, shaun has an odd ring of blood around his mouth, it doesn't look suspicious. so the medical examiner, after an autopsy, decides that the second staudte family death in six months is due to "prior medical issues." >> they're thinking wow, poor family. what bad luck. no one was asking questions. >> reporter: and nobody questioned that story? >> no. >> reporter: even though her husband had died just months before? >> yes. >> reporter: after police leave the scene, rhonda walks over to check on her standoffish neighbor. surprisingly, diane answers the door. >> i said, we just saw the coroner's van was here. are you okay? is everything all right?

and she said, "oh, yeah, my son died." >> reporter: was she distraught? >> no, she said it to me just like that. she said, "my son died." very matter-of-factly. i just was shocked. >> reporter: rhonda may be one of the few people diane talks to about shaun's death. because for him there is no funeral, no memorial, not even an obituary. like his father, shaun is quickly cremated. >> i'm like, oh, my god, this, this mother must be devastated. she lost her husband, now she loses her, her son? >> reporter: now only the staudte women are left. diane, her darling rachel, 12-year-old brianna and sarah living their secluded lives. >> i think they closed the doors even tighter, because you didn't see them outside. i don't know how they even got their mail, because we didn't see them at the mailbox. >> reporter: then the following june, could it be true? the staudte plague strikes again? this time it's sarah.

diane has seen this end badly before, so she takes her 24-year-old daughter to the emergency room. sarah is sick, goes to the hospital gravely ill. >> sarah's in, in very grave condition. it does not appear that she is going to survive. >> reporter: sarah's kidneys shut down. the pancreas and other organs failing. worst of all, her brain is hemorrhaging blood. diane turns to facebook, maybe hoping for divine intervention. "asking for prayers as my daughter sarah is in critical condition." diane's brother-in-law michael staudte is floored by the post. >> wow, it's like a lot of bad luck here in this family. what's going on? >> reporter: a good question. what is going on? >> 911, where's your emergency? >> reporter: finally, someone in springfield, someone claiming to be close to the family, calls in a tip to police hinting that the pious church organist may harbor an unholy family secret.

what did the caller say exactly? >> that diane staudte might be responsible for two or three homicides. again, brought up mark's death, shaun's death being very close proximity to each other. also spoke about the potential that sarah was going to die as well. >> reporter: so the caller was essentially blowing a whistle on diane staudte. >> correct. yes. >> reporter: armed with that anonymous tip, springfield police detective neal mcamis begins investigating. he starts by pulling the reports on mark and shaun's deaths. the uncanny similarities are stunning. >> mark was experiencing flu-like symptoms for several days prior to his death, same type of description with shaun. now we have sarah that's also in the hospital with flu-like symptoms. >> reporter: police are now connecting the dots. then detective mcamis visits the hospital. there he gets more troubling news from sarah's doctor.

performed several tests. they could not find out they what was going on. and he said that he was suspicious that there, it was a possible poisoning case. >> reporter: so your radar goes up? >> definitely. >> reporter: police figure it's about time diane staudte answers some questions. she voluntarily comes to the station and as she enters interview room number three, one of the strangest police interviews we've ever broadcast begins. diane discusses sarah's critical condition. >> i'm looking at the lab reports and it's like you can't be living. her kidneys were shot. she had a brain bleed. her pancreas was acting up. it's bad. >> okay. >> she was as close to death as you could get. >> reporter: her affect may seem strange. but remember this is a woman dealing with great stress, emotionally and financially. and her family is crumbling one by one. >> my husband died last year of a heart attack.

though. >> did he? what kind of stuff did he have? >> oh, he had liver problems. he was diabetic. he wouldn't quit smoking. >> do you have a son as well? >> no, not anymore. he died. he stopped breathing during one of his seizures. >> i've just never heard of anybody dying from a seizure before. is that pretty common? >> it can happen. >> reporter: the detective steps away, but when we come back, he does too, to turn up the heat on the merry widow. >> there's been some things that have come up during the investigation. >> reporter: it's time to learn what really is going on behind closed doors at the staudte home. >> i'm horrible. i'm a horrible mother. >> reporter: stay with us.

♪ ♪ ♪ that's life. you diet. you exercise. and if you still need help lowering your blood sugar... ...this is jardiance. along with diet and exercise... jardiance works around the clock... to lower blood sugar in adults with type 2 diabetes. this can help you lower blood sugar and a1c. and although it's not for weight loss or lowering systolic blood pressure, jardiance could help with both. jardiance can cause serious side effects including dehydration.

, or weak upon standing. ketoacidosis is a serious side effect that can be life-threatening. symptoms include nausea, vomiting, stomach pain, tiredness, and trouble breathing. stop taking jardiance and call your doctor right away if you have symptoms of ketoacidosis or an allergic reaction. symptoms of an allergic reaction include rash, swelling, and difficulty breathing or swallowing. do not take jardiance if you are on dialysis or have severe kidney problems. other side effects are genital yeast infections, kidney problems, increased bad cholesterol, and urinary tract infections which may be serious. taking jardiance with a sulfonylurea or insulin may cause low blood sugar. tell your doctor about all the medicines you take and if you have any medical conditions. so talk to your doctor, and for more information, visit jardiance.com unlimited data from at&t means you can stream it all. like that anthony michael hall movie where he fights with the girl. e one where he gets rejected by the girl. even stream the one where he creates the girl.

anthony michael hall movies you want. i wonder what he's up to these days maybe he's shopping in an at&t store? get unlimited data and your fourth line free when you have at&t wireless and directv. plus, up to $650 in credits to help you switch. un, deux, ♪rois, quatre ♪ crafted with care, for a dry, balanced taste. c'est cidre not cider' into the frozen wilderness. the scent of his jerky attracted a hungry wolfpack behind him. to survive, he had to remain fearless. he would hunt with them. and expand their territory. he'd form a bond with a wolf named accalia... ...become den mother and nurse their young. no... james left in search of his next adventure.

toyota. let's go places. liquid foundation - l'oreal's new lumi cushion. a cushion drenched in liquid foundation. tap on a little for a fresh luminous glow... tap on more whenever you need more coverage. new lumi cushion from l'oreal makeup designer paris. "20/20" continues, with a family plot.

>> reporter: over the course of 14 months, the quiet, god-fearing staudte family seems as cursed as an old-testament transgressor. member after member inexplicably struck down. mark staudte, who fronted a blues band and 26-year-old son shaun both suddenly dead. 24-year-old sarah, lying in the icu, her kidneys and brain failing. now police want to know, is this a matter of bad luck or bad intentions? which is why diane staudte, wife, mom and church organist is sitting in the interrogation hot seat. with cameras rolling, detective mcamis asks about her marriage, and for the first time glimpses a reservoir of resentment. >> we were still married, but it was not what you'd call a good marriage. >> have there ever been any infidelities on either side?

>> he had. he was running around and he would drink and smoke pot. >> he wasn't a very good guy, is what you're saying? >> yeah. even with all his faults, i still loved him. >> reporter: in this police interrogation video, diane reveals cracks in the foundation of the staudte home. >> was there ever any physical abuse towards you? >> no. >> nothing like that? >> i didn't think it was that bad, but my kids would probably say otherwise. i wasn't happy. >> reporter: now watch as he deploys a classic interrogation technique, shifting from inquisitor to sympathizer. >> i'm a believer myself, so i understand where you're coming from on that. >> reporter: he tells diane sometimes even the righteous reach a breaking point. so what happened with sarah? >> as far as did i do something to her? i didn't do anything to her. i guess i could've taken her to

the e.r. sooner, but i didn't know. >> reporter: a major reveal. diane may have delayed taking her daughter to the hospital. >> that was just where her story started to crumble. >> i'm horrible. i'm a horrible mother. >> reporter: then a suggestion that shaun may have been suicidal. but again, she admits she did nothing to help. >> he'd been threatening to kill himself. i didn't want to bother because i was tired of it. i'm such a crummy person. >> now's your chance to tell us why and to show some remorse, ask for forgiveness. >> reporter: then she drops a bomb. >> to put it really short and sweet, i knew they were drinking antifreeze. >> reporter: drinking antifreeze? >> and i was so mad at them, i didn't want to take them in. >> you knew, diane, that they were d

>> i didn't know what else to do. i really didn't. >> reporter: and there it is. after two hours in the box, diane staudte quietly confessing to poisoning her own children with antifreeze. this is a woman who's admitting that she killed her son and tried to kill her own daughter. what are you making of this? >> i was just totally astonished, to be honest. i couldn't believe what i was hearing. there were times i didn't know what to say or how to react. how long had you been giving them the antifreeze? >> maybe a couple of days. >> and what were you putting it in? >> coca-cola. >> how much would you put in? >> couple of teaspoons, maybe. >> reporter: but why antifreeze? she explains that it's easy to get and easy to disguise. the main ingredient, ethylene glycol, a colorless, odorless, sweet-tasting and deadly chemical.

>> killing someone with antifreeze is a classic way to try to mask what you're doing. takes time, it's relatively flavorless, and there are no immediate signs after death unless you're looking for it. >> reporter: now it's all pouring out. a full-blown confession. diane admitting she poisoned her husband mark the exact same way, spiking his gatorade with antifreeze. apparently she'd had it with a husband she considered an abusive deadbeat. >> by then, i hated his guts. he would throw things at me. he would throw things at the kids. and i guess i'd just had enough. >> reporter: killing her husband is awful enough, but a mother poisoning her own children? this mom's motive is downright chilling. >> both shaun and sarah would just basically, i don't know, trash the house. ne

shaun would be interfering with whatever i would do. >> so if he was just a constant bother, wouldn't leave you alone. >> oh, he was more than a bother. >> would a pest, would that be a good word for it? >> no, it was more than that. >> reporter: my husband got on my nerves. i couldn't stand him. and my son, you know, was a pest. i mean, did she seem, like, at her wit's end? >> no. she, again, throughout, she stayed flat. even when this -- when she's telling me that information, she's, you know, she seemed unfazed. >> reporter: unfazed, even by the ultimate kicker, why she poisoned her daughter. >> and then with sarah, you talked about, you know, she wasn't getting a job and she had these student loans and you were going to end up having to pay for them. >> that's pretty much. >> and you just had had it with her as well. >> i'm not a perpetual killer. i'm just stupid. i regret doing it. i really do. i've screwed up everybody.

>> reporter: but it's too late. here come the steel bracelets. >> right now, you're going to be under arrest. >> reporter: case closed? not by a long shot. see, police are about to search the staudte home, and will find a purple diary with some very purple prose. this was a key piece of evidence. it will prove that diane had a partner and eyes on another target in these horror movie homicides. >> oh, my god. >> reporter: next. r chronic pai, you may be sooo constipated it feels like everyone can go ...except you. opioid-induced constipation, oic, is a different type of constipation, which may need a different approach. longing for a change? have the conversation with ur doctor about oic, and ask about prescription eatment options. ♪

and that's just the beginning. we've changed every part of the experience, right down to the samples. now, you can try any shade in any sheen. this is a brave new day, for color. get the best paint for any budget. like glidden® premium paint and primer starting at $17.97. the home depot. more saving. more doing®. dogs - sure can be messy. but with nexgard, their flea and tick killer doesn't have to be. nexgard, the vet's #1 choice for dogs, is a delicious, beef-flavored chew that kills both fleas and ticks. so it's easy to give, easy to take. reported side effects include vomiting, itching, diarrhea, lethargy and lack of appetite.

a history of seizures. why mess around? for powerful flea and tick protection, ask your vet about nexgard. the #1 choice of vets for their dogs and yours. want great whitening without the mess? think outside the box colgate optic white toothbrush plus whitening pen for 5 shades whiter teeth. brush, whiten, go! no mess, no waiting, no rinsing. colgate optic white toothbrush plus whitening pen.

"20/20" continues with a family plot. >> reporter: as the freight trains roll through springfield, missouri, the wheels of justice are turning slowly too. police are interviewing 22-yea

a star student, a gifted musician, and artist. mom's pride and joy. >> mom was there every step of the way really encouraging and cheerleading rachel to be great. >> reporter: but now, her dearest mommy, diane staudte, is behind bars after confessing to the poisoning deaths of her husband and son and the attempted murder of rachel's older sister. >> rachel, can i get you to switch with me? >> okay. >> reporter: police just hit rachel with the news. >> confusion. shock. i mean, that's, nobody expects to have somebody that they know do that. >> reporter: in this interrogation tape obtained by "20/20," detective mcamis lays it all out. demure diane has delicately engineered a ruthless culling of her own herd. only the pious and the productive will make the cut. >> did you think somebody else was going to be next? >> sarah can be poisoned just for sitting around on youtube, i

house. brianna sure as heck doesn't do anything around the house. >> reporter: rachel fesses up that her mom had some unusual reading material. >> we had a book on poisonous plants. she would talk about cyanide. >> reporter: then a crucial -- critical moment across town. these pictures show a house in disarray. this was the home, the second residence. detective mcamis gave us a tour inside with permission from the new homeowner. >> this was sarah's room, there was couches, papers, kind of things streamed about. >> reporter: laptops, flash drives, sculptures, scattered about. and in the garage -- paydirt. >> this is where our crime scene detectives located the antifreeze on the work bench. >> reporter: and right next to the antifreeze, the other compound in diane's cruel chemistry -- an otherwise unassuming six-pack of coke.

was given to both shaun and sarah in terms of poisoning them. >> reporter: the concoction right there? >> yes. correct. >> reporter: the coke and the antifreeze. >> that's it. >> reporter: in the bedroom, a curious detective makes that dynamite discovery. this is rachel's purple diary, haphazardly thrown on a shelf. its contents, a trove of sinister secrets. >> it appeared to be in a journal entry written by rachel, knowing that mark and shaun were getting ready to be killed. >> reporter: so at first, you're thinking this is a mother, an evil mother who's tried to wipe out her family. and now you discover her daughter might be involved helping her? >> yes. >> reporter: that journal entry, dated june 13th, 2011. nearly a year before mark died. it reads -- >> it's sad when i realized how my father will pass on in the next two months. shaun, my brother will move on

it will be tough getting used to the changes but everything will work out. >> reporter: that's pretty chilling. >> very. >> reporter: she's writing in a journal about killing her father and her brother. >> it was extremely alarming. >> reporter: back at the station, detective mcamis leaves the room and gets briefed on that explosive diary. he returns in a different mood. >> rachel, do you recognize this? >> yeah, i remember this. >> reporter: this is missouri. and now it's time to show me. >> you wrote this then, is what you're telling me? >> i had a lot of really bad dreams about them dying. i talked to mom about it and she mentioned she was thinking of hurting them. >> reporter: rachel's bad dream, just beginning. mcamis isn't buying her story or her tears. >> what did you tell your mother? >> that it would be quick. that it'd be easy. >> repor

awful truth. mother's favorite was also mother's little helper. >> when did you guys come up with this plan? >> we talked about it like christmas. >> reporter: she's sitting right here. she started to tell the whole thing. she basically owns up to it. >> to hear the daughter and the admissions that she's making that this was a plan. i was totally shocked, totally stunned by everything that had taken place. it was just a completely surreal feeling. >> reporter: the mother-daughter duo carefully plan and research all options. suffocation, pills, googling how to kill your husband. the devout christians even explored witchcraft. >> on my computer specifically there's a lot of wicca sites. >> reporter: before settling on antifreeze. >> because in general you could put it in something and you couldn't taste it. >> what else did she tell you? >> she wanted a specific tasteless one. >> rachel, whose idea was this? >> mom brought it up and then we discussed. >> mom recruiting daughter to

help her systematically kill her husband, her son, and then poison her daughter? it's almost unheard of. >> reporter: it was supposed to be just dad, but pretty soon diane turned her attention to shaun, the son she thought was irritating. listen to how little it took to end up on her hit list. >> shaun, we argued on a lot 'cause i still think we could have put him in an assisted living, but she wanted him out. >> what did you say when she talked about killing sarah? >> sarah was equally unneeded. we could have found someplace else for her. she was very adamant on that sarah was just a burden, that sarah needed to be taken care of. >> reporter: rachel, too, now under arrest, charged with murdering her father and brother. her sister, sarah, still fighting for her life. when rachel was arrested, there was a big clue in her purse. >> her pur

>> reporter: with her sister sarah hospitalized, rachel had authored a poem evocative of edgar allen poe. >> once upon a time there were six. now there are three. only the quiet ones will be left, my mom, my little sister and me. >> reporter: wow. that's pretty cold stuff. >> this is very cold and depraved murder. >> the springfield poisoning case. two people dead, two in jail. one in the hospital, the family was poisoned with antifreeze. >> reporter: the next day, the tale hits the news like a twister. while down at the county courthouse, a rare sight. a mother and daughter, both arraigned for murder. >> no, way. this cannot be true. not right here in our little neighborhood. >> reporter: but no one is more surprised than mark's old bandmate, charles alexander. >> i was floored. when i heard that he was poisoned, then i just cried, i collapsed. i said, "i can't believe this woman did this."

>> reporter: looking back, he begins recalling little quirks about his friend's wife. >> i was never really allowed in the house, for some strange reason. it was always at the garage. it was so strange, i seen antifreeze bottles sitting in the garage, i'm thinking, who has antifreeze in the summertime? >> reporter: strangest of all, diane's blase manner after mark died. >> i went to her house, and asked her what happened. and she proceeded to tell me, like she was giving me a recipe to a cake. no emotions, no nothing. >> reporter: just matter of fact. >> it was like, oh, he died, and you add two eggs. >> reporter: also shocked, diane's fellow church members at redeemer lutheran. well, maybe except for one. remember that anonymous 911 caller who first tipped off police? do you ever find out who blew the whistle on her? >> we were able to determine that the anonymous caller was actually the pastor at diane's church. >> reporter: the pastor turned her in. >> yes. >> reporter: pastor jeff sippy. >> if you are not praying for

your children, no one else is either. >> reporter: the leader of the flock, compelled by his own conscience to root out the wolf among them. he declined our requests for an interview. so he knew that something was evil here. >> i think he definitely had his suspicions. diane's demeanor after the deaths. he told me couldn't take those feelings that he had to -- he had to call it in. >> reporter: when we come back, two staudtes in jail awaiting trial. two staudtes dead and a third in icu. but this one regains consciousness. and lives to tell. did she suspect that her soda was spiked? she was trying to kill you? she tells her story only to "20/20," next. ♪ you can help prevent blindness

when you get your vitamins at walgreens, you help give life-changing vitamins to kids across the globe. get vitamins here. change lives everywhere. walgreens. at the corner of happy and healthy. what's the husband's name again? david. david! ♪ ♪ ♪ ♪ please, humans first. behold the future. i'll...come back. the veil intelligent toilet, by kohler. when your symptoms start... distracting you? doctors recommend taking ...non-drowsy claritin every day of your allergy season. claritin provides powerful, non-drowsy 24 hour relief... for fewer interruptions from the amazing things you do

live claritin clear. late friday and early saturday... and get tek-gear for the whole family under $10... tees under $10... and shorts and capris for the whole family under $20! plus, take an extra 15 percent or 20 percent off! you'll get kohl's cash too! kohl's.

at giant, shoppers low prices by the thousands, plus a thousand more that just dropped. all these low prices! what are you trying to do, get me to feed the whole neighborhood? no. just trying to save you a whole lot of "bread." [ laughter ] thousands of blue tags, thousands of low prices. my giant.

i'm chris van hollen, and i approve this message. narrator: an attack ad from the campaign for donna edwards. so untrue. so outrageous that president obama said, "pull it down." the obama white house called the ad on chris van hollen and the nra "misleading." the sun says van hollen and president obama have the exact same position. the post praised van hollen as a "leading champion on gun safety," and condemned the edwards ads that "mislead" voters. donna edwards. will she say anything to win an election? "20/20" continues, with a family plot.

a woman who defied all the odds, and lived to tell. surviving a vicious poisoning. >> this is where i sleep. >> reporter: 24-year-old sarah staudte has had to relearn to walk and talk. >> right here. >> reporter: her speech still stunted from the irreversible brain damage she suffered. tonight for the first time, she's speaking out about the horror and betrayal. sarah lost her father mark suddenly in 2012 and brother shaun just five months later. you found him dead. >> yes. >> reporter: that must have been horrifying. >> traumatizing. >> reporter: and more traumatizing, learning that her mom diane was not her protector but a predator. poisoning them all with antifreeze. and the icing on the cake, her younger sister rachel was part of the plot. >> i was asking, why? why did my mom and sister kill my dad and brother, and harmed me? >> reporter: did you belve

can't be true. >> i assumed that it wasn't true. they were innocent people, being blamed. >> reporter: but any trace of sympathy evaporates after sarah reads in the newspaper why her mother poisoned three family members -- she simply despised them. >> they really planned this heinous crime. i was shocked. i just felt like i wanted to strangle my mom, because of what she did. >> reporter: the big question, why did diane bother to rush sarah to the hospital after leaving her son and husband to die at home? in a follow-up interview with a clearly rattled rachel at the green county jail, detective mcamis wants to know. >> when sarah got so bad, why did you take her to the hospital? >> reporter: was it some last minute tug of christian conscience? apparently, no. >> i didn't want another one to die in the house. >> and why is that? >> because houses are nasty after somebody's died in it.

i get a lot of nightmares. >> reporter: but what rachel tells police next may be the most heinous of all. she and mom diane weren't exactly finished. >> brianna, was she next? when were you guys going to kill brianna? >> some time after sarah. >> reporter: brianna. the youngest member of the staudte clan. a tender 12 years old, too young to drive, but old enough to drink her mother's poison, antifreeze, in her root beer. they were going to kill the little girl as well? >> 12-year-old girl. >> reporter: what's wrong with these people? >> what was the reason for brianna? >> because i know there's no way in hell i'd be able to take care of her. i can't take care of me, so how could i ever take care of her? >> she had described brianna as a burden, they didn't want around the house. that was their explanation. >> reporter: four people, they would've killed four people in this house if they could've? >> correct. rachel said that her mother was the only one that understood her.

and it was just going to be those two. >> reporter: do you think this was just a case of a mom and daughter who just in some sick way wanted to have a simpler life? >> i don't think there's going to be any acceptable remotely rational explanation. the question is, how could this have possibly happened? >> reporter: did the police blow this thing? could they have prevented sarah's poisoning by connecting these dots? >> i think it's easy to go back now. there was nothing, at that point, to indicate anything malicious. neither one of them knew about the other deaths. >> reporter: and what about the medical examiner's office, who critics say bungled the bodies of mark and shaun by missing obvious signs of foul play? they defend their work on the case. >> when you have physical findings at the autopsy which match the story that was given, typically other organs aren't looked at microscopically.

>> reporter: saying antifreeze is difficult to detect unless you're looking for it. later tests did confirm that shaun's body had the presence of the killer chemical ethylene glycol, found in antifreeze. that news came a bit late for sarah. still, she's learned to accept her new reality, living in an assisted care facility. more alone than ever. do you still consider them family? >> not anymore. i consider them as killers. who hate me. >> reporter: you're angry. >> i feel like i want to slap both of them, and calling them "b" words. >> reporter: their family plot uncovered, perhaps it was to be expected that the mother-daughter murderers would eventually turn on each other. and sure enough, rachel made a last-ditch effort to save herself with a plea deal. >> reaction to a guilty plea from rachel staudte, the springfield woman charged with poisoning three of her family members. >> reporter: throwing her mom under the bus. >> that's crucial.

the fact that her daughter has pled guilty, seems ready to testify, could in and of itself be enough to convict her and potentially send her to death row. >> reporter: when we come back, diane staudte in court. and for the first time, the daughter she poisoned coming face to face with her sister and mommy dearest. what would you say to rachel, and to your mom? the whole day to sell to the their old cart aside and buy a new one... oops.

guess you'll just have to see a movie... ...then get some dinner. what a pity. now becomes skinactive. new garnier skinactive clearly brighter. the active daily moisturizer with antioxidant vitamin c that smoothes, boosts radiance and protects. see brighter skin in just one week. new clearly brighter from garnier skinactive. jane loves to treat herself. so she loves new light & fit crunch. greek nonfat yogurt with delicious toppings like chocolate and almonds. now that's a treat! light & fit crunch. feel free to enjoy. headache? motrin helps you be an unstoppable, let's-rock-this-concert- like-it's-1999 kind of mom. back pain? motrin helps you be the side-planking, keeping-up-with- your-girlfriend- even-though-you'll-feel-it- later kind of woman you are. body pain? motrin helps you be an unstoppable,

l-in-one-trip kind of woman. when pain tries to stop you, there's motrin. motrin works fast to stop pain where it starts. make it happen with motrin liquid gels. un, deux, ♪rois, quatre ♪ crafted with care, for a dry, balanced taste. c'est cidre not cider' >> reporter: judgment day for diane staudte. she enters the courtroom, her back against the wall, facing death by lethal injection. but then -- >> you intend to enter a plea of guilty in this case. >> yes.

killing her husband and son. sentenced to life in prison without parole. also in court, in the front row, the daughter she tried to kill. 24-year-old sarah facing her mom who poisoned her with antifreeze. >> i prefer to be survivor than a victim. she not only took away my dad and brother but she took away my independence. >> reporter: callous to the end, diane never bothering to look at her damaged daughter. yet weeks later, when it's rachel's turn to be sentenced, she dissolves into tears. reading a statement to her sister. >> i'm sorry that i couldn't find the courage to stand up for what was right. your suffering could have been prevented and i hate myself for not being there for you. >> reporter: and yet for all the pain and loss, today sarah says she harbors no ill will. >> i forgive my mom. >> reporter: how

in yourself to forgive her? she tried to kill you. >> yes. >> reporter: when we last spoke you said that you would want to slap them. you'd want to call them the "b" word. >> right. not anymore. >> reporter: what changed? >> as time went by i matured. >> reporter: she smiles fondly when sharing photographs of a life that seems like a distant memory. >> that little boy here is my brother shaun. that's me. >> reporter: you're such a cute little girl. a family gone. but not forgotten. what are you fondest memories of hanging out with your dad? >> i love going to concerts with him. >> reporter: mark staudte's music may have been more prophetic than poetic. just listen to the lyrics of his final song, "female judas." ♪ your kiss of betrayal baby it done and did me in ♪ >> reporter: to this day, bandmate charles alexander, still hearing those lyrics in his head.

>> i just wish i could've helped him. i wish i could've saved him. who would do that to their family? why? there's bad relationships everywhere, but you don't destroy your own family. >> rachel, that accomplice, was sentenced to life in prison. >> our question, how could a mother have influenced, even brainwashed a daughter like rachel? let us know, use #abc2020. i'm david muir. >> and :

kimberly: breaking news, two firefighters in critical condition after being shot, a civilian also wounded by gunfire. alongootings happened sheridan road in temple hills. we have team coverage from the scene and the hospitals.