tonight on "nightline," judgement call. 911 tapes raise new questions about a 6-year-old girl gone missing from her bed. frantic mother. >> i didn't even come and check on her. >> and a seemingly calm father. >> i need to report a missing child. i believe she she was abducted from my house. >> a whale tale. friendly, playful and the size of a school bus. >> say hello, "nightline." >> but now it appears these gentle giants are in deep danger. and being billy bob, he's steamed up the screen with halle berry in monster's ball, tlid us

in sling blade, his real life, including a marriage to angelina jolie, has been just as dramatic, but tonight we meet the real billy bob thornton. good evening, i'm bill weir. if a parent has just discovered that their 6-year-old is missing from her bed, how should they sound when they call for help? that is the question swirling around the father of is bell cellis who can be heard chuckling on a newly released 911 tape moments after discovering his little girl's empty room. could it be shock? or a tell-tale clue? how much can a 911 call reveal about guilt or innocence? ryan owens asked the experts to find out. >> reporter: it's the closest many of us ever get to a crime scene. >> 911 emergency.

>> reporter: a call that can be crucial to investigators. >> reporter: an eyewitness report caught on tape. >> i want to report a missing person. >> reporter: and it's the latest clue in the abduction of isabelle cellis. that's the desperate voice of her mother moments after she found out her little girl vanished. >> who noticed her gone? >> my husband. i went to work this morning at seven. i didn't even check on her. >> rebecca cellis was working as as a nurse when her husband sergio said he went into the 6-year-old's room and discovered her bed empty, the screen off her bedroom window. >> oh, my god, somebody took the window out of our house. >> reporter: from day one, and this is day 25, the parents' story has not changed.

>> just please, please -- >>r. >> reporter: together they have pleaded for her safe return. her father sergio, seemed special lea emotional. >> we're looking for you isa, we love and you miss you so much. and we will never give up looking for you. >> reporter: that emotion noticeably absent on the day of isa bell's disappearance. in the 911 call he made first before his wife made it home from work. >> hello, i need to report a missing child. i believe she was abducted from my house. >> why do you think she was abducted? >> i have no idea. i woke up my sons. we looked everywhere in the house and my oldest son noticed that her window was wide open and the screen was laying in the backyard. >> it's not just his calm voice, but the joke he seems to crack. remember, he said his daughter just disappeared.

>> she just left for work, and i told her to get her butt home. >> you have to be careful reading too much into that, but clearly his comfort level is perhaps a little odd, but you can't really interpret it beyond that because we all react to stress in different ways. >> reporter: which is joe vega's point. >> he's a great father. >> reporter: he's a close friend of sergio. >> sergio has a good head on his shoulder. >> tucson police released the tapes just days after he was banned from seeing his two other children. detectives will only say they have no suspects in the 6-year-old's abduction. >> hello, i need to report a missing child. i believe she was abducted from my house. >> reporter: so what might investigators glean from these tapes? turns out, there's a science to it. forensic linguistics. the authors of a study published

in an fbi journal, examined hundreds of 911 calls and say guilty callers tend to be calm, polite and patient, have a defendant mentality, often asking, if they will be arrested, even apologizing. and have little or no variation in their speech and make no demands for help. >> you cannot say that one behavior during a 911 call is evidence of guilt or innocence. >> professor robert leonard is a linguistic who has analyzed 911 calls in high-profile cases. >> even when you're saying, does someone sound guilty, what you're really asking, are they matching the patterns that are expected of a person in this situation? >> reporter: he points to this call made by 17-year-old marty tank lef. >> this is marty tank less, 33 seaside drive in bell ter. i need an ambulance.

it's an emergency. >> he woke up in his new york home to find his parents had basketball stabbed. >> he begins by giving his name and asking for an ambulance to come to his address. he does not begin with what people would standardly expect in a 911 call when your parents are bleeding to death. >> reporter: one of several factors that helped convince detectives and then a jury, he was the killer. he spent 17 years in prison before he was exonerated. an important reminder, what you think you hear on these 911 tapes, isn't always what happened. with that in mind, searchers were back in the arizona desert tonight, looking for any sign of 6-year-old isa bell cellis. they left empty-handed again, nearly a month after she vanished and her parents first called 911. i'm ryan owens for "nightline" in tucson. >> still holding out hope for

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thanks to high school english, we know it was two things that drove captain a hab's relentless pursuit of the white whale -- revenge and oil. while burning blubber no longer lights our homes, some are concerned the ocean's gentle giants could once again be threatened by man's demand for oil. abc's cecilia vega sploins how, for our series, into the wild. ♪ >> reporter: there's a

peacefulness, a calm in baja, meax. that is until a creature the size of a school bus pops out of the water to say hi. >> wow, that's amazing. look at his eye. he sprayed me in the face. >> reporter: it doesn't take us long to figure out why locals call them the friendly whales. it's a role reversal. this is not a place where tourists come to chase the wildlife. it chases us. they're like puppies. the young calves in particular seem to love the cameras. >> hello, you're not shy. we were talking about you. are your ears burning? yes, your ears are burning. then there's that, the little token of friendship they like to leave behind again, and again. so much for the shower this

morning. a small price to pay for these breath-takingly close encounters. >> nobody bo bothers them. it's regulated. their curious nature comes out. >> while their home may be protected, environmentalists are concerned about a looming threat in their other home. each year, these whales migrate from the lagoons of baja, to their feeding grounds in the arctic, where shell oil is scheduled to begin explore tore drilling this summer. >> the oil and gas lease overlap with the critical feeding area of the gray whale. >> that has environmentalists lightning lee henry, up in arms, because it turns out that whales literally talk to one another. deep under water, they call out, emitting sounds like this. it's how they find food, findimates and how mother whales keep in touch with their young. the process for looking for oil,

means sending sonic booms, or shock waves into the ocean's floor, creating some of the loudest man-made noises. >> when you have all this noise mavenging their ability to hear, it's like them trying to lead their daily lives with a bucket on their head. >> reporter: leafing them disorient disoriented, separating mothers from their young. shell declined our request for an interview but said their drilling will not harm the whales. they claim the bow head whale population has grown despite feeding in their grounds. but it's not just the noise environmentalists are worried about. some say shell is not prepared if the unthinkable were to happen again. >> if you look at what happened in the gulf of mexico, we weren't prepared to clean thaup in pristine conditions. it's unreasonable to think we'll be prepared to clean up an oil spill in the arctic.

obviously shell has insurmountable resources, and we'd like them to step up and take responsibility. >> shell says they have, adding in a statement, it also assembled an oil-spill response fleet that is second to none in the world. environmentalists remain skeptical and hope to generate enough public support to delay, even halt the drilling in the arctic, but they have their work cut out for them. the obama administration has already approved it. >> this is not an easy battle to fight with gas prices approaching $4 a gallon. >> absolutely. and it's a short-term answer. what are we going to do after we drill in the arctic? it's a short-term solution to a long-term problem. and we need to be looking at alternative fuel sources. >> reporter: in the meantime, researchers are gathering as much information about the whales as they can. they use cross bows of all

things to gather small samples of flesh that will tell scientists how healthy the whales are. they use underwater equipment to record their sounds and exhaustive photo identification to keep tabs on the whales. >> is that the official scientific test? >> yes. >> our new friends enjoy a few more weeks in baja before heading north to face an uncertain future. >> oh, look, he's opening his mouth. >> yeah, you can see. >> >> can i touch it? >> sure, you can. he won't mind. >> we'll have to wait until next year when the whales return to see if they're as healthy and happy as they are today, that is, of course, if they come back here at all. i'm cecilia vega for "nightline" n baja, mexico.

>> just ahead, we wooed halle berry on screen and married angelina joel ne real life. we'll talk to the man himself next. ♪[music plays] ♪[music plays] purina one beyond. food for your cat or dog. on my journey across america, i found new ways to tell people about saving money. this is bobby. say hello bobby. hello bobby. do you know you could save hundreds on car insurance over the phone, online or at your local geico office? tell us bobby, what would you do with all those savings?

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that's all the horses sir. ...and the men? all the king's men are here too sir. it doesn't look good. ♪ a bit of hollywood trivia. what oscar-winning writer can barely read? that's billy bob thornton, and his struggles with dyslexia is one part of his life. there are bizarre eating phobias, that marriage to angelina and a creative life still burning bright.

>> reporter: he bedded halle berry, one of hollywood's sexiest women, in monster's ball. offscreen, he married one of the world's sexiest stars. >> i call it a kaiser blade. >> reporter: between sling blade and bad santa, he's become one of the most controversial and unlikely stars, yet he's remained something of a mystery. to set the record straight, he sat with friends telling stories, which turned into his new book. in it he admits to a lot of strange behavior that drives his creativity, his dyslexia, his fear of medieval furnitiure, kim odo dragons, even silver wear. >> reporter: so what do you eat with in a restaurant? >> i don't go to many restaurants, but i'll ask for plastic wear. >> everybody says there's a fine line between genius and madness. >> i don't know if i'd call myself a genius and i don't think i'd call myself mad

either, but there's definitely a connection between creativity and some of these, wreafr you call them. but frankly, the phobias, aren't as big a deal as people make them out to be. >> reporter: he's a charming eccentric. perhaps that's what angelina jolie fell in love with when they met on the set of pushing tin. she was just 24. he was 20 years older. their personal lives became fodder for tabloids with talk of dark behavior. >> we were supposedly vampires who had a dungeon, and we drank blood. we didn't even wear blood vials. she bought these clear lockets. we literally poked each other in the finger with a pin and rubbed a little bit of it on that locket. >> how did you blow it? >> i blew it because i didn't think i was good enough for her.

>> reporter: he said his lack of self-esteem contributed to their split. a drama teacher convinced him he had talent, which brought him to hollywood, but he lived hand to mouth for years and wound up in the hospital for starvation. >> reporter: how long did you not eat for? >> for a couple of weeks. >> reporter: but even at big box office hits, he's been obsessive about food. he said he ate nothing but a ka of tuna and lick ris every day for this movie. >> i weighed 128 pounds on pushing tin. i'm six feet tall. i kind of went overboard. >> reporter: that's an eating disorder, isn't it? >> yeah. i always felt like i was the phantom of the opera. >> reporter: he's working on his fourth album with the box masters, a rocka billy band he tours with.

he sees himself as an artist and rails against the cheap twitter and youtube created celebrity. >> turning our society in a caddie, cynical, judgemental place and it's killing art. because as a result of it, we're losing the magic. >> reporter: today he lives a quiet life in beverly hills with his long-time girlfriend, connie and their daughter bella. >> how are you? >> my rock'n'roll kid. >> reporter: his teenage son from an earlier marriage says the eccentric man is a regular dad. >> he's the most normal dad you'll ever meet mp. >> reporter: normal in what way? >> goes downstairs, makes lunch, watches football. we have awkward talks about girls every now and then. >> reporter: that's about as normal as it gets. >> his book, written with the great kinky friedman, in stores