tonight on "nightline." eyes wide open. tossing, turning, imagine being unable to sleep ever. that medical mystery can be a deadly reality. tonight, we investigate what happens when you're always awake. plus murder in paradise. a mother of two killed in cancun and her tv producer husband, the main suspect. now as the investigation reveals an alleged mistress, her family prepares to bring their loved one home. and invisible man. he is a gravity master of international fame with celebrity clients like brad and

angelina. his true identity remains a mystery. we're hot on the trail of the ill usive artist. good evening, i'm cynthia mcfadden, from a rainy new york city. we begin with a topic on many people's minds at this time of night. sleep. everyone needs it, but these days most of us don't seem to get enough of it. 40 million americans are said to have sleep disorders. sleep deprivation remains a torture. imagine never being able to sleep. it's rare but when this extreme form of insomnia strikes, it can result in a complete shut down of the body. >> reporter: you're looking at a man who hasn't slept for months.

his name is silvano. in this video, he's neither awake or asleep. >> he's a very sick looking man who hasn't slept for months. >> reporter: he suffered from a sleep disorder called fatal familial sleep disorder. it's a brain disorder that destroys the mind's ability to regulate sleep. a former dancer, he could no longer move normally and he was tormented by his inability to rest. months later, he slipped into a coma and died. his case proving that he can die. we know even less about why we sleep. >> reporter: we do know that sleep repairs the damage we do to our brains everyday, whether it's working too hard, drinking too much of or simply living. >> you can think of the brain a bit like you think of a muscle. during the day, there is all this activity going on, but you need a time when the brain is

quiet so that it can repair and rebuild just like muscle does. >> reporter: for people with ffi, that quiet time never comes. the part of the brain regulates sleep. the thalmus functions like a traffic light. because of the destruction of the thalmus the person can't go to sleep. >> this woman is preparing for her wedding day but her father won't be walking her down the aisle. he and eight other relatives died of ffi. >> there was memory issues and muscular issues and it progressed and progressed. >> reporter: meagan fears she could be next. she has a 50% chance of inheriting ffi but has chosen not to ache a blood test to

learn her fate. >> i would put a time line on my life and i'm not sure i could live like that. finding out i don't have it would make my life incredible but if i found out i did, it might ruin it. >> reporter: ffi is sleeplessness in its most rare form. >> an individual who has sleep deprived himself for one single night is as impaired as somebody who is legally intoxicated. >> reporter: dr. bornemann is one of the top sleep experts in the country. i think in general, americans are getting sleepier. i think our culture is based on a 24 hour culture, so i would imagine that until we start to see these trends change that this will only continue to get worse. >> reporter: dr. bornemann agreed to help us test the effects of sleep deprivation.

our admittedly less than scientific experiment began two days earlier when i skipped a night of sleep. i am on my way to the sleep clinic and i've been up 24 hours straight. definitely feeling it. when i arrived, dr. bornemann tested my concentration and memory. he had me repeat numbers from lowest to highest. >> one, two, three, four, six -- eight, nine. >> reporter: he asked me to recite a long list of words from memory. >> watch, strand. insect, watch. i said that already, didn't i? >> this is it. >> here you go. your night in the sleep lab. >> reporter: a technician connected electrodes to my body.

>> 462. >> reporter: really. they measure everything from brain wave activity to leg movements and breathing patterns. i'm wired up and ready for a restful night sleep. i've been up for 38 hours at this point. i'm ready to knock out. the sleep lab's cameras recorded me through the night. every toss, every turn. over the course of hours, i dipped in and out of rem sleep. as morning came, it was clear my body had needed the rest. >> this has been a pretty consistentent consolidated period of rem. it is approximately 8:45 in the morning. >> good morning. hi. >> reporter: when i finally woke up, i didn't know what time it was. i'm going to guess 7:30. >> try again.

>> reporter: 8:00. >> try again. >> reporter: 6:30. >> it is 10:30. >> did i sleep that long? >> you are a free man. >> what a night! morning. >> rather good afternoon. >> yeah. >> reporter: the extra sleep seemed to help. one, two, four, five, six, seven, eight. i aced my concentration and memory test. dime, cave, deck, male, bank, couch. >> not only did you get 100% right, but in the absolute correct order how i told you. >> verbatim. >> there were no red flags for my night of sleep. no sleep disorders, senatoring problems or insomnia. >> you were expressing rem sleep even 8:00 in the morning, 10:in

the morning. >> you are saying i have the body clock of a lazy college student. >> absolutely. your words, not mine. >> reporter: in fact, dr. bornemann says when we sleep is determined by our dna. many of us try with coffee or energy drinks. >> lack of sleep can kill. it is a doorway into the mysteries of sleep as well as the importance of sleep. >> reporter: which brings us back to silvano, the man who died because he couldn't sleep. for him and other ffi victims, sleeping wasn't a choice. for the rest of us, it isn't one either. this is erik hong for "nightline" in minneapolis. sleep problems come at a steep price. an estimated $16 billion alone.

when we come back, an american mother found dead at a cancun resort. her husband the suspect. we have the latest on this murder mystery. we didn't think dog food... could make that big of a difference, but it really has. we thought, oh, goldie, you're getting older, and she started eating the purina one... and people would say, "what did you do to her?" [ announcer ] purina one for seniors unlocks the brilliance of nature. [ kristen ] it's a great feeling having a beautiful, happy dog., it makes you feel like you've done something good for your pet. [ announcer ] it's amazing what one can do. now, reformulated with... enhanced botanical oils... that naturally nourish... to help sustain a bright mind. moments you'e looking forward to... what if they were .stolen from you? by alzheimer's. this cruel disease costs americans more than $170 billion a year, and could cripple medicare in the near future.

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♪ it's so m'm! m'm!good! ♪/. . next, a tragic murder case that's attracted international attention. it sounds like a made for tv movie, a hollywood executive and his family vacationing in mexico when the mother goes missing and

is then found strangled to death. authorities believe the marriage had gone sour and there are reports of screams coming from the couple's room. is he the killer? nearly a month after the crime, still no arrest. what, we wondered, had happened in paradise. it was to have been a family holiday on the beach in cancun. a mexican vacation for hollywood producer bruce beresford-redman, his wife monica and their two little kids but it turned into a nightmare. on april 8th, monica's 42nd birthday, her body was found in a sewer at the resort they were staying. today, her family had the painful task of claiming her body. they will be flying it home to california. her sister, jean. >> my sister is no longer here and i'm not going to be able to call her and talk to her and see her. it's horrible. it's so hurtful, i can't even

express how much pain is inside my body. >> reporter: but who would want to kill the mother of two? her husband was a successful producer, such shows as cbs's survivor, and mtv's pimp my ride. he says his wife left the moon palace resort to go shopping on monday, april 5th and never came back. by tuesday, he flew the children home to california and reported his wife missing. telling a los angeles television station he was very hopeful someone will find my wife very soon. still, she hasn't been located and we're looking. but according to mexican police, his story doesn't add up. the night before she disappeared, several guests at the resort say they heard fighting coming from the couple's room. one guest reportedly heard a woman screaming for help and there's no record of monica leaving the hotel to go

shopping. security guards checked all cars entering and leaving. >> i knew that something very wrong had happened. because my sister would never in one million years leave her kids a whole day with the father without her cell phone. >> reporter: family members say the mexican vacation was planned to help the couple sort out problems in their marriage, including that he allegedly had a mistress. >> they had a rocky relationship and i think that was fairly well known, and we know that there was in fact a mistress. and we have provided all the information that we have to the authorities and we're hoping that all areas of this case will be looked into. >> reporter: tmz posted this photograph last week of bruce with a woman named joy pierce quoting multiple sources who say she and the former survivor producer had an intimate relationship. radar online obtained copies of

e-mails between beresford-redman and pierce. last week the family delivered those e-mails to prosecutors in mexico. one from bruce read in part, "i didn't feel i would be happy without you and that i was going to leave my family so that we could be together. i'm not proud of the way i conducted this." all of which led mexican authorities to bruce beresford-redman, the man they say is their main suspect. though he's not in custody, he's been told he could not leave mexico until the investigation is completed. >> we love my sister and we want justice. we want to make sure this is going to be accomplished. >> reporter: meanwhile monica's family is frustrated that no one has been charged with her murder. over the weekend they held a rally at the brazilian restaurant monica owned demanding justice. >> we want the person that

murdered my sister on this terrible way doing something to a mother that didn't deserve, i want this person in jail to pay for the rest of his life for what he did. >> reporter: the two people who will undoubtedly pay for the rest of their lives are only three and five years old. their children. the body of monica beresford-redman could be returned to the u.s. as early as tomorrow. as for her husband, he must remain in mexico until the authorities have completed their investigation. when we come back, an international man of mystery, his gra feetty art made him a star, but who is the one they call banksy? [ male announcer ] fact: every time you take

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we turn now to the art world and the public and often political drawings of a political master. he's known as banksy. he's unquestionably famous but at the same time unknown. just last week, san francisco woke up to what appears to be six banksy originals. so who the private man behind these public works and how does he make a living? nick watt is hot on his trail in tonight's "sign of the times." >> reporter: i'd call this one of the stranger sights of recent days. crowds gathered at the l.a. premier of a movie made by a faceless graffiti artist from england.

>> what do you think the appeal is? >> i don't know how to answer this. >> reporter: he's exhibited in london and l.a. he's collected by bran je lien na. >> you would be looking to pay half a million dollars. >> reporter: he's made political statements at disney land and on the wall that keeps palestinians away from israelis. he's made countless statements elsewhere, but no one knows who he is. >> you didn't deal with banksy directly? >> no, i've never met banksy. i have no idea who he is. it could be you. >> reporter: we went to the east end of london in search of his early artwork, the street that first made him famous. >> a little from here up. it's still here if you look hard enough.

♪ >> reporter: and it's getting more and more valuable. >> we saw an opportunity and took it. >> reporter: bradley bought this wall and spent nine days removing it, thousands of dollars moving it. banksy won't authenticate it. >> we understand that. that isn't to say there isn't a market for it. >> reporter: for sale, half a million dollars. >> if it is, i'm surprised no one stole the door. most bank banksies are left to fade. the bbc has searched for him. >> we have established that as a teenager he grew up in a quiet

suburben street. the people who live here don't want their property identified. >> reporter: robin banks,ers here's a four-year-old photograph of him. banksy after negotiations with one of his handlers agreed to have a chat over e-mail i'm assuming you will never reveal your identity. why not? >> after a few hours, a reply. >> i haven't gone public because i don't want to go to court. i don't want to get prosecuted and most of all, i don't want to disappoint people with my miserable face. >> he was certainly the grimiest person i ever met. he had a layer of dirt on him under his finger nails on his face. >> reporter: elizabeth was an intern when banksy was in the pub. >> people think i'm one of two people that have met banksy.

i'm sure tons of people, millions of people have met banksy. they just thought he was a handyman and didn't think anything of it. >> apparently his parents think he's a house painter or so the myth goes. >> why do you do what you do? >> i try to make pictures of work with their location and have some kind of point, but the main satisfaction comes from just getting away with it. >> reporter: in this his first mother, banksy explains why he turned to sell lloyd, why he turned the camera on a french man who tried to make a movie on his search of banksy. >> it was built to last hundreds of years of the it's cast in bronze or canvas. but street art has a short lifespan so it needed documented. >> i think this is him right here. >> reporter: is he in this crowd

at the premier? >> were you at the premier last night? >> i didn't go to the premier. i'm not much of a people person. >> reporter: what banksy has achieved in our celebrity obsessed is a magnification of his own sesht by hiding from it. >> i heard he's like six grior a gorillas. >> reporter: i'm sick watt for "nightline" in london. nick watt searching for his own banksy. when we come back, goldman sachs gets ready for its day with the senate sub committee. here's jimmy kimmel with what's coming up next. >> jimmy: thanks, cynthia, meagan mullally, erin andrews and two 13-year-old scrabble champions are here. will i conquer them for

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