tonight on "nightline," devil's playground. the chilling secret tape shot by the most reviled couple in america. >> let me see. i bet you can go down really sy, huh? >> husband and wife duo who kidnapped and raped jaycee dugard. the untold story about how they evaded justice for so long. gluten free nation. you've heard of fat free and sugar free. but gluten free? celebrities swear this fad diet boosts their energy, but now doctors are raising questions about its safety. plus, shark bite. an incredible story of survival. the ocean's fiercest predator, and the recent spate of attacks on humans. they're closer than n u think.

>> announcer: from the grow ball resources of abc news, with cynthia mcfadden and bill weir in new york city, and terry moran in washington, this is "nightline," august 2nd, 2011. >> good evening, i'm terry moran. the story of jaycee dugard shocked the nation and revealed the failures of the nation's legal system in deeming with sexual predators. kidnapped when she was just 11 years old, jaycee dugard was held captive for 18 years. a sexual prisoner of phillip and nancy garrido. probation officers repeatedly visited the home but they never found the missing girl. well, tonight, the prosecutor in this case has released disturbing new home movies that show how the older woman here, nancy garrido, stalked and videotaped other little girls to fulfill her husband's perverse desires. david wright brings us the story from california for our series, "crime and p pishment."

>> reporter: convicted child rape is phillip garrido used to play guitar in playgrounds. his wife working the camera would zoom in on the kids. she was more than just the loyal wife of a sociopath. >> you got me real good? >> yes. >> it certainly appears she was involved in procuring the girls for his delight. >> reporter: she was his partner. his sidekick. his pimp. >> like this? like this? >> reporter: today, prosecutors released a new video from the backseat of her van as she coaxes a young girl to do the splits. >> let me see. i get you can go down real easy, huh? >> yeah, that's easy. >> let me see it. >> cajoling a young girl to perform on video for phillip jar reredope's sexual perverted satisfaction. >> reporter: nancy garrido was clearly y ery bit at perverse as

her sick husband. >> making videos. look what i did for you. i'm doing for you. and when she pleases him, she gets confirmation of being a good girl. >> reporter: today, prosecutors released a portion of her interrogation in which she admitted she did this more than once. >> a a we talking less than 20? more than 20? >> it's got to be less than 20. >> reporter: all of those kids are victims. any of them could have ended up like jaycee lee dugard. >> does it say record still? >> yeah. >> reporter: two years earlier, they kidnapped the 11-year-old dugard. incredibly they held her hostage for 18 years. as jaycee lee dugard told diane sawyer -- >> it seems impossible now that no one knew you were there. >> doesn't it? >> it seems impossible. >> i know. >> reporter: impossible, not least because phillip garrido was a known sex offender, sentenced to 50 years forape but released early after serving

just 11 years with glowing reports from prison psychologists. >> unquestionably the most disturbing mistake of the criminal justice system was the release of phil garrido in 1988. >> reporter: a mistake compounded by incompetent parole officers who visited the garrido's home dozens of times while jaycee dugard was a prisoner there. >> if you have any questions, come into the office between 8:00 and 5:00. >> 60 times. they may have been just feet from your door. >> yep. >> unbelievable. >> reporter: the electronic monitoring bracelet garrido wore on his ankle showed how much time he was spending in the backyard prison he built for dugard. but none of the parole officers, who were supposed to be keeping an eye on him, ever bothered to look. they filed glowing reports about him, noting his relationship with his wife, his growing and changing in a healthy manner and remains supportive and strong.

in hindsight, it's perfectly obvious their relationship was anything but healthy. >> this is a highly disturbed, very primitive woman who is so psychologically dependent on this man that she would do his bidding. >> mr. messner? >> reporter: abc's chris cuomo tracked down some of the parole officers for answers. >> we just want to ask you a question. >> reporter: they didn't have any. according to new details released today, garrido violated his parole several times but not sent back to jail. he tested positive for drugs, submitted watered down urine samples. in 1993, he finally did land back in federal prison for failing a drug test and nancy garrido became jaycee lee dugard's only jailer. >> whole month he's gone. >> yeah, she said he was on an island with a friend. but he was actually sent back to prison. >> so, just the two of you. >> yeah. she would lock us in every

night. she wanted to watch this scary movie called "the unborn." it was awful. it was very scary. >> reporter: august '93, her husband, fresh out of jail, again. nancy garrido was out trolling the playgrounds. that's when this video was taken. >> show me your split, did you? let me see it now. >> want to see -- show you? >> yeah. >> reporter: the little girl spots the hidden camera. >> this is -- light is on. >> no. i don't know anything about that camera. >> reporter: nancy covers it up. >> within a few days after being released, that videotape is made by nancy. all the while, they have a 12-year-old girl locked in their backyard. >> reporter: parents tell their children all the time not to talk to strangers. this is why. i'm david wright for "nightline"

in los angeles. >> monsters. thanks to david wright for that disturbing report. up next, the government is monitoring this, celebrities are doing it, but is it safe for you? coming up, the debate on the gluten free diet. ♪ all righty. oh, oh. you are a little biscuit. i'm carol. uh, we should skedaddle 'cause it's girls' night. so...okay. oh, wow. you got a skinny-dipping scene after the duel, right? well, i -- shh, shh, shh. show. don't tell. [ male announcer ] your favorite movies right when you want them. just a little -- okay. oh, wow. [ male announcer ] watch unlimited tv episodes and movies instantly through your game console or other devices, all for only 8 bucks a month from net [ carol ] this could turn me into a history buff. all for only 8 bucks a month from net

naturals from delicious, real ingredients with no artificial flavors or preservatives. naturals from puria cat chow. share a better life. , woman: day care can be so to save some money, i found one that uses robots instead of real people. 'cuz robots work for free. robot 1: robot 1: sfx: modem dial-up noise woman: flaws? yeah, um, maybe. anncr: there's an easier way to save. anncr: get online. go to geico.com. get a quote. 15 minutes could save you 15% or more on car insurance. and off we go! seeking inspiration from the world's best yogurts for activia selects in paris we discovered the inspiration for a totally new yogurt. activia selects french so silky and smooth with lots of juicy fruit. then our search took us to beautiful greece and this thick and creamy greek yogurt, so rich and full of flavor.

it was a grueling trip! try new activia french and greek yogurt. a world of great new tastes.

>> announcer: "nightline" continues from washington with terry moran. for some people who suffer from a genetic condition called celiac's disease, eating starchy foods that contain the protein gluten can make them sick. but a gluten-free diet has

recently become a fad unto itself. today the fda announced they would publish guidelines for labeling foods gluten-free. but is this diet safe for everyone? we found out for our series, "you are what you eat." it's a hot celebrity diet trend. everyone from victoria beckham to gwyneth paltrow's doing it. what is gluten-free? legally, there's no definition. gluten is a protein found in wheat, barley and other grains and many processed foods, soups, salad dressings and sauces, too. and as the diet has become more popular, a wide variety of gluten-free products has been showing up on the shelves of your grocery store. >> this is my, like, special refrigerator. i feel like my name should just be on here because this is where i hang out. >> reporter: we went to whole foods with elizabeth hasselbeck, one of the co-hosts of "the view." she's written a book called "the g free diet" and she's a big advocate. >> everything from bread crumbs

to cookies to bagels. it's there. pie crust is there. >> reporter: hasselbeck has celiac's disease. that's a genetic disorder that causes an intolerance to gluten. so all those foods with wheat, barley, and rye were making her sick for years. until she found out. >> my main goal always is trying find gluten-free food that tastes like i remember it tasting. >> reporter: and she claims it's not as restrictive as it seems. the great thing about pasta -- >> is that you can have it if you're celiac or gluten-free. >> reporter: and that's important to you? >> so important. sono italiano. i grew up in an italian household. pasta was at our table like another family member. i like to say, instead of removing, you want to actually just replace. >> reporter: hasselbeck is a true believer in a gluten-free diet and not just for people with a genetic disorder like she has. she encourages people to try it out. >> you still have to make sure you are eating a balanced meal. but those that are adopting this for fashion or trend, they're going to probably like it. they're going to see that there

are many more options than they thought. >> reporter: do you think i'd be better off reducing or eliminating gluten from my diet? >> i think that if you gave yourself a challenge where you went gluten-free, you would find that your energy levels would soar and that you would like how you felt every single day. >> reporter: but after we spoke with hasselbeck, we went up to columbia university medical center and spoke with a doctor who knows all about gluten-free diets. he says there's no scientific evidence to support all the claims in hollywood and elsewhere about gluten-free living. are there benefits for a person who doesn't have celiac disease in adopting a gluten-free diet? >> not that i'm aware of. >> reporter: not only that, but there's no guarantee of weight loss. and it's likely bad for you to cut out all gluten. comparatively few people have celiac disease, about 1 in 100. and doctors who are very familiar with the diet say that going gluten-free can be dangerous unless you are one of

the minority of people with that disease. >> i see some very famous people telling me that this is a healthful way to eat. it sounds healthy. what's wrong with it? >> well, a gluten-free diet is not entirely healthy. often it lacks fiber, and the manufacturers of wheat flour fortify wheat flour with vitamins and minerals. >> reporter: popularized by a scene from "gossip girl" -- >> the pie has been secured. thanksgiving no longer needs to be canceled. >> reporter: babycakes bakery in dodotown manhattan is filled with gluten-free goodies. from cakes to donuts to brownies and cupcakes. so what's not in your cupcakes? >> there is no gluten. no dairy. no eggs. no soy. no refined sugar. no preservatives. >> reporter: so how do you make a cupcake? >> well, we start out with the cupcake base, which is made of

garbanzo, fava bean flour, potato starch, arrowroot. we use agave nectar instead of sugar, apple sauce instead of eggs, coconut oil instead of butter. and somehow it tastes good. i don't know how it happened. >> reporter: it's those missing nutrients that make a diet entirely devoid of gluten unhealthy for most people. >> it's been demonstrated that if you're on a gluten-free diet long-term, you can actually become b-vitamin deficient. and we often see people, they often restrict calcium as well, and people may become calcium deficient. >> reporter: but for those who suffer from celiac disease and for their families, a place like babycakes is a godsend. >> throw these in the fridge if you don't eat them right away. okay? >> we get a lot of episodes of mothers crying because their children can finally choose whatever they want. it's a moment definitely for them because their kids have been without desserts for so long. it's just a really special

thing. >> reporter: and that's the best thing about this latest dietary fad. while it's not for everyone -- >> i think i'm going to do a caramel crunch. >> okay. >> and then i'm'm going to have dessert. >> reporter: for millions of people -- >> it's good, right? >> it's really good. >> reporter: life's getting a lot tastier. >> have some coffee with it. >> i'm going to be a regular. >> it was good. up next, how one city coped with a spate of grisly shark attacks on people. and one man's incredible escape from the jaws s a man eater. ♪ [ male announcer ] the davis twins... ...are alike in nearly every way... ...right down to brushing their teeth. so how did only one get gingivitis? well, one in two people do. so i told karen about new crest pro-health clinical gum protection toothpaste. it helps eliminate plaque at the gumline, helping prevent gingivitis. it's even clinically proven to help reverse it in just 4 weeks. and it protects these other areas

dentists check most. looks like the twins are even again. new crest pro-health clinical toothpaste. life opens up when you do. you can take the heat. 'til it turns into heartburn, you've got what it takes: zantac. it's strong, fast lasting relief. so let them turn up the heat. you can stop that heartburn cold: (sssssssss!!!) zantac. what if we designed an electric motorcycle? what if we turned trash into surfboards? whatever your what if is, the new sprint biz 360 has custom solutions to make it happen, including mobile payment processing, instant hot spots, and 4g devices like the motorola photon. so let's all keep asking the big what ifs. sprint business specialists can help you find the answers. sprint. america's favorite 4g network. trouble hearing on the phone? visit sprintrelay.com. there's another way to minimize litter box odor: purina tidy cats. our premium litters now work harder to help neutralize odors in multiple cat homes.

purina tidy cats. keep your home smelling like home. [ female announcer ] sweet honey taste. 80 calories per serving. 40daily value of fiber. i'm here in the downtown area where the crowd is growing.

[ female announcer ] watching calories at breakfast never tasted this sweet... i'll go get my bowl. [ female announcer ] ...or this huge. new fiber one 80 calories. yes, you can actually love breakfast.

affect over one million homes each year. without regular maintenance, septic tanks can back up, causing a disgusting mess and countless hours of repair. introducing new rid-x septi-pacs. easy-to-use dissolvable pouches that help prevent disgusting septic back-ups. the powerful dual action formula has enzymes to immediately break down waste and time-release bacteria that work continuously to reduce tank build-up. use rid-x once a month and help save yourself from disaster. rid-x. number one in septic maintenance.

some steps are infested by rats. other by bedbugs. but sydney, australia, has a bigger problem. sharks. dozens of people have been attacked in recent years. and stephanie sy reports now about how science has helped the city deal with aer if reshus neighbor. >> reporter: shark attacks have become a predictable part of summer from the u.s. coast, where there have been at least a dozen attacks this year to sydney harbor. smack dab in australia's largest city. this attack is caught on camera. fortunately, diver paul lived to tell about it. >> the shark just started shaking me. as soon as my right hand came out of the water, i noticed that it was gone. >> reporter: three attacks in three weeks spread fear in the

city. >> they're calling it the shark play. a sudden surge of attacks and sightings across or coastline. >> it's a great white! >> reporter: the two other victims are surfers. >> authorities say people shouldn't panini >> reporter: sydney's waterways are prime hunting grounds for the world's three deadliest shark species. great whites, tiger and bull sharks. since a ban of commercial fishing, the number of fish in the harbor has increased and all that prey may be attracting more sharks and more attacks. >> lisa is in a serious condition with sere vie injuries. >> reporter: it appears lisa was attacked by an over ten-foot lolo great white. >> only one bite. my head and arm with in its mouth. all i could see was blood. >> reporter: she's lucky to be alive. a week after lisa was bit, another surfer, dave, was attacked at dusk. >> blood was going everywhere.

squirting five, six foot out. >> reporter: his wounds, likely the work of a bull shark. the frequency of attacks led the government to launch an unprecedented scientific investigation to find out if it's more dangerous than ever for swimmers. researchers set about finding and tagging as many sharks s as they could, as quickly as possible. the team slips the hooked shark upside down, putting it in a state of temporary paralysis. >> wow. three meters. 30. this is nearly a full-sized bull shark. >> reporter: now, they can tag the shark, performing on the fly surgery off the side of a boat requires nerves of steel. >> just do one more stitch. >> reporter: the researchers attack a special camerer to one shark, recovering the footage later. based on the tagging efforts,

bull sharks are teeming in sydney's waters. >> we have 25 in the harbor in one summer. >> we can see from this, the sharks are utilizing all the harbor. >> reporter: the sharks traveled nearly 20 miles a day through the most popular swimming spots. on the busiest beach holiday of the year,, seven sharks cruised right past thousands of swimmers. the large number of sharks and the relatively low number of attacks on people led the scientists to a somewhat reassuring conclusion. >> so, it does jug zest that there are humans and sharks co-existing, happily. >> reporter: but with more sharks drawn to heavily populated waters, the threat remains. >> i'm not happy about being eaten by one, you know? that's life. this is our world and everything has its place here. >> reporter: for "nightline," i'm stephanie sy in new york. >> "shark invasion" airs