[ cheers and applause ] >> huncho jack. ♪ this is "nightline." >> tonight, the deadly mudslides in california. homes and cars swept away. at least 13 reported killed. rescuers pulling this 14-year-old girl from a mound of muddy rubble. >> it's our worst fear coming to life for us right now. >> scenes of destruction from inside the danger zone. >> there are at least two other houses on this block that have completely disappeared. >> how last month's wildfires paved the way for today's crisis. plus, undercover high. adults posing as students capturing the private lives of teenager

semester. >> parents have no idea what's going on in high school. but now they will. >> confronting issues of sexuality, social media, and cyber bullying and something more sinister than anyone expected. >> they were talking about what they would do to me, get me drunk, then they'd rape me. >> but first, the "nightline" 5. number 1 in just 60 seconds.

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good evening. thank you for joining us. we begin tonight in southern california, with those devastating mudslides. just weeks after wildfires tore through the region, today's staggering rainfall triggering the deluge that has already killed at least 13 people. the damage is shocking with waves of mud ripping up trees and homes, shutting down a major freeway. here's abc's matt gutman. >> reporter: tonight in california cars, homes, and lives swallowed by those deadly flash floods and mudslides. >> we have multiple reports of people trapped. >> it's our worst fear coming to life for us right now. >> reporter: at least 13 are reported dead. two dozen missing. scores more are injured. this 14-year-old girl pulled from the muck. authorities still in search and rescue mode, fearing those casualty counts will almost certainly rise. >> the only words i can really

looked like was it looked like a world war i battlefield. it was literally a carpet of mud and debris. >> reporter: it was a natural disaster officials say that was exacerbated by the thomas fire, the biggest in california history, which blackened hillsides and stripped them of anything that would absorb tuesday's deluge. up to five inches of rain pounded the region. the water coming down sometimes at a rate of more than an inch an hour. >> the carpenteria fire department has a rain gauge that recorded .54 inches in just five minutes. >> reporter: searching through creek beds with titanic force. >> the water came through this dam, destroyed several vehicles and that rv there. >> reporter: overnight the famed 101 freeway overrun. >> we're retreating here, and you can actually feel debris hitting our car right now. >> reporter: closed for 30 miles in both directions. >> you can see how fast that water is moving here. i mean,

water. >> reporter: then around 4:00 a.m. a catastrophic flow of mud and debris rushed towards homes. >> you could start to see some mud starting to come down, and so right then i told my wife and the dog to get up on the bed. and i thought it would be a good idea to push on the door, which didn't really last very long. so then i ran and jumped on the bed and basically in seconds it was as high as the countertops. >> reporter: emergency crews on rooftops and dogs padding through debris, searching for signs of life. >> our people are out there trying to do the best work they can and perform as many rescues as they possibly can. >> reporter: those rescuers sometimes trudging through mud that was chest high in the frantic search for the missing. >> you think someone is in there? >> we have a strong feeling someone's in that house. trying to use our sonar equipment to hear voices. >> reporter: so you think the person inside is still alive? >> not sure. >> reporter: but hope. >> yeah. >> reporter: about a mile away

of these boulders, gives you a sense of the power of the water to just heave these giant trees and giant rocks down stream. and it was there that robert riskin appeared. slogging through hip-high mud, light was fading and he said so was his hope of finding his mother. >> i'm just in shock at this. this is unimaginable. i honestly -- it's hard to -- i'm just in shock. >> reporter: robert and his friends alone in this field of debris and despair. >> this house was perfect. always. it's who she was, you know. who she is maybe. i don't know. >> reporter: we left them as they debated whether to go home or keep searching through the night. >> we've been searching and calling and i just hope that she's -- was fast and she's not hurting. >> reporter: all day helicopters and high water vehicles ferrying families like ben hyatt's to safety. >> i was worried it was just going to keep coming and comi.

i woke up my wife, and we just did not know what to do because we were just surrounded by mud. >> reporter: but some unable to escape the path of destruction in time. >> so we had a wall of mud that must have been at least eight to ten feet high. >> did you actually see it coming towards you? >> yes. and the boulders. >> and it stopped, basically, at our kitchen. and then two other neighbors also ended up, a brother and a sister, in our house also. >> and they had lived up farther away. >> and the sister didn't make it. >> they were washed up against your house? i'm so sorry. >> it's a huge tragedy. >> reporter: a huge tragedy for a place that is still reeling from those disastrous fires that burned parts of this area all through december. >> well, the fire was the ultimate extenuating condition. then the rain that hit so hard so fast was yet another extenuating condition. so we have two unusual occurrences happening at the same time.

that? >> reporter: last month the thomas fire ripped through this region, scorching over 280,000 acres of land. turning freeways into fiery hellscapes, reducing neighborhoods to cinders. >> i honestly can't even describe what i'm thinking. my mind is not even really connecting with it all yet. and yet there it is. >> reporter: and forcing tens of thousands to flee. >> these helicopters are dropping as much water as they possibly can on these fields. the idea is to stop the fire from getting from this charred part of the mountain down there to those avocado fields and the homes below. >> reporter: ultimately, that blaze denuded mountainsides pretty much of what could have absorbed that water overnight into ash. tonight an eruption of support on social media. celebrities who live in montecito and santa barbara like ellen, rob lowe, and gigi hadid tweeting out their thoughts and prayers for their hometown. but for the

toiling tonight it's luck that they need. >> so when you have the mudslide, everything's kind of wet, the dogs can sniff in there, get in there pretty easily and you can still pull people out of the mud. the problem is that mud is going to harden quickly. >> reporter: feverishly working against time and hoping to find some more survivors. for "nightline" i'm matt gutman in santa barbara, california. next -- the undercover experiment. adults posing as high schoolers, exposing the dark underbelly of students and social media. having moderate to severe plaque psoriasis is not always easy. it's a long-distance run. and you have the determination to keep going. humira has a proven track record of being prescribed for nearly 10 years. humira works inside the body to target and help block a specific source of inflammation that contributes to symptoms. in clinical trials, most adults taking humira were clear or almost clear and many saw 75% and even 90% clearance

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ask a teenager what high school life is like these days and you'll probably get a one-word answer. fine, good, whatever. but to find out what's really happening beyond the eyes and reach of adults a team of recruits went undercover posing as students and filming a semester of private interactions, revealing shocking truths parents need to know. here's abc's deborah roberts. >> cops. drugs. >> reporter: one high school. >> i don't think adults really get how hard it is to be a teenager right now. >> reporter: seven new students. one big secret. >> would you be willing to go back to high school undercover to find out what teens are facing today? >> did any of you ever find yourself for a moment thinking what the heck am i doing here? >> yes. >> reporter: these young-looking 20-somethings went undercover as students at highland park high school in topeka, kansas. >> parents have no idea what's going on in high school. but now they will. >> i'm not use

this early. >> reporter: george and lena are siblings from georgia. he says he was bullied in high school for being gay. >> i was a target. >> reporter: she was a cheerl d cheerlead cheerleader. >> hopefully i'm able to help these kids with my own experience. >> reporter: 22-year-old nicolette from new mexico was a teen mom. >> people ostracized me. >> reporter: and daniel, a youth pastor who struggled in high school with a learning disability. >> how do you overcome something? even the little things that are happening in your personal life. >> reporter: they're all a part of a&e's new docuseries, "undercover high," which sheds light on challenges today's kids are facing. like sexuality, bullying, and social media. >> these are things that are real issues for kids, and i believe that this series is going to give opportunities for dialogue between youth and adults. >> was it sort of a gotcha idea? we're going to put some adults in there and see what we can find on these kids? >> yeah, no, absolutely not. the intent wasn't gotcha.

the teen bubble? how do you see at their level what is going on and how conversations happen? how does social media work? >> reporter: the students thought they were being filmed for a report on high school life. only a few administrators knew the truth. each undercover adult was given a new identity, transforming themselves both physically -- >> the term brace face comes to mind. >> your new cell phones with a new social media profile. >> reporter: and virtually to better fit the part. >> it's harder to be a student today versus when i was a student because at school you would worry about, okay, what table am i sitting at? what group do i fall into? now you have what kind of social media do i post? who follows me? and it doesn't just end at school. it continues, you know, when you go home. you're basically being judged twice. >> reporter: in fact, a recent national survey found that 94% of american teens ages 13 to 17 use social media. >> and even begin to tell you how many times these kids

phones. it's a bigger distraction now than it was then. >> reporter: the undercover idea has been seen before. remember "21 jump street"? >> you'll be going in as undercover high school students. >> my name is josie. >> reporter: or "never been kissed." >> where are you going? >> to high school. because i'm a high school student. >> reporter: but this is not a movie. the participants sometimes facing very real and unexpected threats. >> i feel like it's normal for new girls to get a lot of attention. and it's just because it's a fresh face. >> reporter: in her first weeks at school lena became the center of attention for a group of young male students. they sent her friend requests and messages. >> there's this group. they accidentally added me. oh, my goodness. these kids had literally spent like a whole afternoon talking about me. >> reporter: but that attention quickly spiraling out of control. >> maybe that's their plan, like get you to hang out with them and get you all drugged up.

conversations, it got a little bit more serious. >> they are talking about raping me. >> that is something serious, girl. >> i know. >> honestly, it was just really overwhelming reading it. they were talking about what they would do to me, they would get me drunk, then they'd rape me. >> they were plotting to rape you? >> yes. honestly, i felt like as an adult it put me in a place where i was like oh, my goodness, am i doing something wrong? am i dressing wrong? so i can only imagine what these teenage girls are going through. >> reporter: after investigating highland park administrators found out those involved in the group chat were not from their school. yet the scare was revealing. one survey showing that 34% of kids ages 12 to 17 report being victims of cyberbullying. >> what surprised you the most about what's happening in our high schools and what teens are dealing with today? >>

be said enough the impact of social media. >> and phones were everywhere. >> everywhere. and i do not see the phones being everywhere as some failure at highland park. phones are everywhere in every school that i went to to look at this, and it is the smartphone. the smartphone changed everything. >> reporter: the undercover experiment was delicate, since high school relationships already fragile were no doubt heightened in this case by the fact that only one side knew the true nature of the friendship. >> hey, listen up. listen up. >> reporter: senior deandre phillips was one of the popular kids at highland park high, an athlete and class president. he befriended george, opening up to him about a very personal secret. >> i can't do certain things because i have like a reputation. >> at school. >> yeah. >> yeah, you do have a reputation. but are you really being yourself? >> no. >> no.

about being bisexual, you know? >> that was a really big show of confidence and trust for this student to talk to you about that. >> for some reason he actually told me that he trusted me more than anybody in that school. and to me it was a little shocking because he was the school's president, he was, you know, a jock. >> was that hard for you to do and then once you found out that he was an adult -- >> i would say it was kind of confusing to me because i really haven't told any people here about my sexuality and like this is a new person that for some reason i feel comfortable. with that being said, knowing he was an adult, i just -- i felt kind of sad in the moment because now he has to go away because -- >> because the project is over. >> yeah. >> you exposed some pretty personal moments and lives in this show. were you worried at all about putting these kids in a difficult situation? i mean, they're vulnerable. >> i

something as sensitive as somebody confronting their own sexuality, before we put that on television we really wanted to make sure on as many levels as possible that the student was in a place of comfort with that. >> you've been that one person i could talk to. >> reporter: the cameras and premise of the show may have complicated an already complex time for these teens. but former principal dr. beryl new says it opened a window too. >> i think that there is a culture that is below the surface that adults don't always notice. and i think, you know, the social issue may be that parents will have some fodder for discussion that's meaningful. >> reporter: for? like d'andre, these relationships, though brief, have had a lasting impact. >> this show has helped me realize kind of my purpose in life. i really want to help people and like help them grow. so i decided to change my major. i want to start off as a

become a principal. >> so you want to go into education because you did this program. >> yes, ma'am. they really helped me a lot. like i feel like i'm a completely different person. you know, starting the show to now. >> reporter: for "nightline" i'm deborah roberts in topeka, kansas. >> "undercover high" airs tuesday nights on a&e. and next, a view from the middle ground of north and south korea. could today's historic talks be a step toward peace? ok, so with the award-winning geico mobile app, our customers have 24/7 access, digital id cards, they can even pay their bill- (beep) bill has joined the call. hey bill, we're just- phone: hi guys, bill here. do we have julia on the line too? 'k, well we'll just- phone: hey sorry. i had you muted.

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♪ and finally, rare talks were held today between north and south korea in which the north agreed to send an olympic delegation to the upcoming winter games in pyeongchang. the two countries agreed to speak further about reducing military hostilities along their shared border. abc's chief global affairs correspondent martha raddatz is in south korea tonight. >> reporter: as the north korean delegation crossed the border and took a step toward cooperation, further along that border the signs of war are everywhere. this is a military checkpoint near the north korean border and a reminder of how heavily fortified this area is. these are landmines showing people what to look out for. history is written on these roads. the brooding fortifications. if there was a north korean advance into south korea, the legs of those barriers would be blown off. the bigger part would fall i

the road to try to block the north korean advance. the fallout shelters here clean, bright, secure. built to shelter a village. if war comes, they're ready. and while many of the south koreans we met wanted president trump to cool his rhetoric, drop all that talk of fire and fury and get down to negotiations, up here attitudes are harder. me byong oak is 75. she remembers seeing the dead bodies of north korean soldiers as her family fled the north. but if you drive south away from the border, past the bunkers, past the barbed wire, past camouflaged artillery pieces pointing north, you find this. life, music, laughter. here on these frozen waters at the annual ice

the people of wa chen were so focused on catching the trout below they barely seemed to notice the attack helicopters patrolling the skies above. and while few think the surface warmth that was on display in the truce village will lead to a permanent thaw, any kind of crack in the ice is a reason to smile. for "nightline" i'm martha raddatz in guachen. >> our thanks to martha. and thank you for watching "nightline." as always, we're online 24/7 on our "nightline" facebook page. thanks for the company, america. good night. >> today on our show, another player will embark on a quest for a seven-figure payday. will they rise to the occasion or crack under the pressure? we're about to find out on "who wants to be a millionaire." [cheers and applause]

♪ [cheers and applause] welcome to the show! are you guys ready to play "millionaire" today? [cheers and applause] i am too. our first contestant is ready. he's a father of three from houston, texas. please give it up for eugene byon. [cheers and applause] all right, eugene, you ready? >> i want to be a millionaire, chris! >> well, let me tell you how that's gonna happen. >> okay. >> 14 questions, the money values growing from $500 all the way up to that $1 million. [cheers and applause] you have your three lifelines. you know what those are about. >> yes, sir. >> all right, if you're ready, let's play "who wants to be a millionaire." [dramatic musical flourish] it all starts with your $500 question. here it is. a word you might find in a negative tripadvisor review, which of the following terms is commonly used to describe a rundown hotel? is it...