this is "nightline." tonight, the big bet. can you put your money where your mouth is? >> cross my fingers. >> this dieter thinks she can, and she's willing to place real money on it. we're along for the extreme six-month journey. can she lose 40 pounds in order to win thousands of dollars? and is this the future of dieting? plus, the danger at the check-out counter every time you use your card. from gas stations to your favorite fast food restaurants, potential predators can get their hands on your money. but what happens when we track them down? and tonight the mystery in new york city. police are investigating how two white flags appeared on top of the brooklyn bridge where american flags are supposed to be flying. how'd they get up there? and why? but first, the "nightline" five.

number 1, in just 60 seconds.

good evening. in a country obsessed with losing weight, tonight a novel and controversial approach. it involves combining dieting with gambling. i'm not making this you have. there is a real company that will bet you that you cannot lose weight. and if you succeed, you can make

thousands of dollars. so is this the future of dieting, or is it just trading one addiction for another? here's abc's linsey davis. >> what do you guys think? >> beautiful. >> reporter: when you're a size 14 -- >> the dress is on. >> reporter: -- the thought of standing next to a bride who looks like this can be daunting. >> my hips are too big. >> reporter: but christina maher is up to the challenge. >> i'd really like to be a size 10. cross my fingers. >> reporter: to shed all those pounds christina is quite literally putting her money where her mouth is. >> i started the diet bet three months ago. >> reporter: each month she pays $385 to healthy wage, a company that allows you to place a bet that you can lose the weight. the wager -- if she loses 40 pounds in six months, she'll win $5,000 plus get all her money back for a grand total of

$7,310. >> i am now down 20 pounds, which is great. and so i have another 20 to go. >> you have a goal. >> reporter: but if christina doesn't lose the weight, she's out thousands of dollars. >> i really need to get myself into gear so i can win this bet because i cannot afford not to. >> reporter: with all her money on the line, this could be just the ultimate motivation to shed the pounds. but can she do it? according to studies, people using money as a motivator are five times more likely to reach their goal weight. could this be the future of dieting? >> betting for weight loss is like betting on your retirement at caesars. >> reporter: not according to dave zinzanko, fitness expert and author of "eat it to beat it." >> people go on these short-term like diet crashes and then they immediately want to reward themselves at end of it and they do that with a bag of oreos. >> reporter: healthy wage says

it's already paid out more than $2 million in prize money. yet only 1/3 of participants actually win their bets. >> in our view there's always a win somewhere. i mean, the people who -- the number of people who make a bet and then just fall off the radar are very few. almost everyone loses some weight. the question is are you going to accomplish your goal? >> reporter: christina's hoping she can beat the odds and actually win. her weight has been a lifelong struggle. >> i remember being 6 years old and thinking that i was overweight. i got on a scale and thinking i was fat. >> reporter: at her heaviest she was 295 pounds. >> you tried everything. >> everything that you can imagine. i almost feel like i'm such an expert on losing weight. it's just the actual follow-through that i, you know, struggled with over the years. >> reporter: after a promising start two months after the trip to the bridal salon christina's only dropped eight pounds. >> i have another 12 pounds. i need to be 194 pounds to win the bet. >> and how much time do you have to go? >> i have a little bit more than a month.

>> reporter: but she's fallen off the wagon a few times. >> i'd have a cookie. and then i'd have a whole package of cookies or i would eat an entire pint of ice cream. >> reporter: so with just one month to go, christina has to kick her diet into high gear, eating only 1,600 calories a day. >> i literally weigh to the gram of pretty much everything. >> reporter: she opts to track her weight online by recording every calorie she consumes. and tracks every step she takes with a fit bit. >> i have 4,034 steps right now. >> reporter: the weight is coming off. >> i used to wear this as a shirt. now it comes down to almost my knees. >> reporter: but as far as she's come, it may not be enough. >> 206.8. it's a little bit higher than it was yesterday. >> reporter: but can christina lose enough in time to win the bet? remember, more than $7,000 is on the line. two weeks later, christina is riding high. she lost 34 pounds in 5 1/2

months. >> i've been going a little low carb and a little bit lower calorie. so now i'm eating closer to 1,200, 1,300. >> reporter: restricting her calorie intake, christina has scaled back her workouts. >> that's why i've been walking in the park a lot and getting in as many steps as possible. >> reporter: and powers through her hunger pains. for now it's still fruit and water. >> what's the first thing you're going to eat when the bet is over? >> a slice of pizza and a piece of ice cream cake. >> reporter: four days later, the moment of truth. she weighs in at 193 pounds, winning the bet with one pound to spare. >> what did it feel like when you stepped on that scale? >> relief. and excitement. looking at the scale and seeing my progress, i couldn't believe it. and i was so happy. >> reporter: christina's weigh-ins were all self-reported, which means healthy wage is taking her at her word. >> you couldn't really just rely on somebody's video. maybe they cheated the scale somehow. >> we're pretty good at

detecting cheaters and making sure that everybody is actually losing weight and not trying to cheat and get money. >> reporter: we met up with christina a few weeks later at the gym, and healthy wage is also here to hand-deliver her winnings. >> you won your bet. so here's your check from us to you for $7,300. >> all the work that i did for this money, it's -- this is really big. >> reporter: but three weeks after reaching her hard-earned goal of 194 pounds she gets back on the scale. the number isn't pretty. >> what does it say? >> 211. >> so it's what, 16 pounds -- >> 16 pounds in about three-plus weeks. >> reporter: gaining back more than a third of her weight loss in just a few weeks. >> short-term solutions are never the best solutions. you want a plan that helps you be successful over the long haul. >> reporter: although they don't tell you what to eat, healthy wage says they do offer guidance and support. >> obviously we can't control people but our content and all

our motivational tips and e-mails all revolve around losing weight in a consistent long-term way. >> reporter: but despite her weight gain christina says she isn't worried. >> it's going to be fine. it's going to be back in no time. i'm sure of it. >> i'm betting on you. >> reporter: for "nightline" i'm linsey davis in new york. and coming up here on "nightline," the hidden danger at the check-out counter. we'll show you how easy it is to have your credit card information stolen and the unlikely savior now riding to the rescue. s mary, a woman who loves to share her passions. grandma! mary has atrial fibrillation, an irregular heartbeat not caused by a heart valve problem. that puts her at a greater risk of stroke. rome? sure! before xarelto®, mary took warfarin, which required monthly trips to get her blood tested. but that's history. back to the museum? not this time! now that her doctor switched her to once-a-day xarelto®, mary can leave those monthly trips behind. domestic flight? not today! like warfarin, xarelto® is proven

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tonight a high-tech scam that is increasingly common, incredibly easy to pull off, and

could be inflicted upon you by the friendly face at your local gas station or fast food check-out counter. police are now turning to an unlikely source to bust these bandits. and here's abc's rebecca jarvis with another look at skimming. >> reporter: he may look like an ordinary mcdonald's drive-thru attendant. but he's actually a brazen credit card thief caught on tape. >> i would have never pointed my finger at the drive-thru because you're sitting right there. you're watching them use your card. >> reporter: let's see that again. he's swiping an unsuspecting customer's credit card not once but twice. first the legitimate charge for the food. then again on a separate device called a skimmer that allows crooks to steal your credit card info from right under your nose. a lesson richard norris learned the hard way. >> he had gotten me three different times. >> reporter: he had never given much thought to his morning

ritual stopping at mcdonald's -- >> may help you? >> reporter: -- for his guilty pleasure. >> can i have a large sweet tea, please? >> reporter: until he and his wife noticed mysterious charges popping up on all three of their credit cards. >> so he was able to skim all three cards at the same location. >> reporter: those golden arches. when the cops checked the security camera, paydirt. >> they actually were able to catch the individual sliding the card and then grabbing the receipt and handing it to me all in one nice movement. you'd never know that he was doing anything wrong. >> reporter: this unabashed face-to-face banditry is more common than you think, and it's not just restaurants. from atms to gas stations, wherever you swipe, criminals could be cashing in. just ask detective jeffrey marshall of the nassau county police department in new york. >> little device. >> that little device. could fit in the palm of your hand. you never see it. in the pocket. and the waitress's apron. you don't know. >> reporter: these days some electronic skimmers are so

advanced that they don't even need a human to operate. >> he takes the device out of the backpack. >> reporter: detective marshall showed thus video of a crook modifying an atmnside a convenience store. watch as he places a fake card slot that contains a skimmer over the real one. >> in four seconds he has it attached. >> wow. >> reporter: but he's not done. he then adds a tiny camera to catch you entering your pin. you'd use this atm and that cheat has enough intel to shop with your credit card and make cash withdrawals straight from your account. this is the skimming device, right here. >> yes. >> reporter: a scam so easy to pull off detective marshall let me try it for myself with the deactivated skimmer he confiscated. >> if i were a criminal and i walked up, this is all i would have to do? >> yep. >> reporter: of course we removed the device immediately. so how do the cops stay ahead of the high-tech crook curve? turns out they're getting help from an unlikely source. >> the atm cashing was the

easiest and best way to make money. and i was making thousands of dollars a day in cash doing that. >> reporter: dan dephillippe is a reformed credit card hacker who got busted and switched sides to avoid prison time. he spent two years training agents in the dark art of skimming. dephillippe's favorite target -- gas stations. installing gadgets like this one inside the pump. >> so this is the reader that would be inside the gas pump. so you would just swipe it through and it would read it right here. nobody would know the difference. >> reporter: when investigators at the arizona department of weights and measures -- >> we're here checking for skimming devices. >> reporter: -- found a skimmer inside this gas pump, they decided to fight fire with fire. >> we inserted one of these little nightvision spy cams in the back of the dispenser. >> reporter: and bingo. here's the view from that camera inside. apparently showing a man and a woman team caught red-handed. >> what we have here, we have

the guy. and i have the missus. >> reporter: they start bickering when they can't find any of their devices. >> it's almost like a husband and wife team arguing about wherever their skimmer is because somebody got it. and that was us. we got it. >> reporter: law enforcement is still on the hunt for mr. and mrs. skimmer. but in the meantime there are some things you can and should do to protect your digits. if you're fueling up choose a pump near the attendant. crooks prefer to operate in the shadows. or you can always pay in cash. at the atm give the machine a good look. if anything appears off, keep on walking. and always remember to cover your hand when you enter your pin. lastly, no matter where you are, check your account. a lot. once you report a fraudulent charge, the law says you have no responsibility for paying charges you didn't make. it worked for richard norris back in florida.

thanks to his careful monitoring, that mcdonald's drive-thru attendant pled guilty and got two years probation. and norris still heads to mcdonald's every morning for his sweet tea fix. >> thank you. have a nice day. >> reporter: for "nightline" i'm rebecca jarvis in westbury, new york. up next here on "nightline," the mystery transfixing america's largest city tonight. who climbed the brooklyn bridge and put up these white flags? and why? but first, a dangerous journey, following migrants across the rio grande. you've reached the age where you know how things work. this is the age of knowing what needs to be done. so why let erectile dysfunction get in your way? talk to your doctor about viagra. 20 million men already have. ask your doctor if your heart is healthy enough for sex.

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when people swim across the rio grande to come to america, they are wading into dangerous currents, open sewage, and often water snakes. tonight, a look at the crisis along our southern border that you've likely never seen before. here's jorge ramos from our sister network, fusion. >> reporter: i'm on the rio grande. mexicans call it rio bravo, the furious river. and this day it feels like a -- patrols, masked men on fast boats carrying high-powered firearms. they're ready for anything. and so am i. >> the second they go out of their house it's a very dangerous journey for them to cross illegally into the united

states. >> reporter: the rio grande, 1200 miles of water between the u.s. and mexico. the point of no return. 33 immigrants have died crossing over just in the past nine months in the laredo area alone. murray salas is the supervisory agent for the border patrol in laredo, texas. >> the currents are very strong, especially underneath. if there's any rocks, any debris, any potholes when people are crossing, they're going to payne. once they panic, they're going to get in trouble. >> reporter: it is clearly very dangerous for an adult. what would it be, a river like this, for a kid? >> it would mean death. >> reporter: since october last year an estimated 57,000 children have made the treacherous journey from central america headed to the united states. double last year. increasingly, the river has become a dangerous cross-roads. this 15-year-old from honduras crossed the river just a few days ago. were you scared of swimming the river? you were scared.

orbin, which is not his real name, says he escaped from his violent home town, san pedro sula, to make his way to the border and into texas. his mother lives in florida. it took him 25 days traveling alone with no help. why did you leave honduras? orbin told me he had to leave because the gangs threatened to kill him. >> this is the way that immigrants come to the united states. and you can see all the traces, once they get into the water, as you can see, they use all these kinds of plastic bags to protect what they have. the little that they have. >> reporter: to find out what these central american immigrants endure under the supervision of many border patrol agents, my producer and i decide to cross the river. in some places the river can be as wide as 600 feet.

strong undercurrents push us at least 200 yards from our starting point. and we remember the agent's warnings about debris and other dangers. we swim all the way to the mexican side and back. >> just imagine what would it be for a kid, 8, 9, 12, 13 to try to cross this river by himself. >> reporter: it takes us about 20 minutes. for those who make it to the other side, this is just the beginning of an arduous journey. many will end up in detention facilities to be deported. as for or bin, he's trying to avoid deportation back to honduras. >> he's 15. he's incredibly courageous. >> yes. >> he did it all by himself. what happens to him if he goes back? >> he was telling me how his friend was also threatened as he was to join the gang and because he did not want to join the gangs they killed him. so that's what really made him snap and say i have to do something because i'm next if i don't join the gangs.

>> reporter: a deportation for orbin would be a death sentence. which is why they continue to risk crossing the furious river. for "nightline" i'm jorge ramos on the rio grande. >> fascinating report. our thanks to jorge for that. and before we leave you tonight, a note about the mystery in new york city this evening. as we speak, the nypd is on the hunt for whoever's responsible for this strange sight on top of the brooklyn bridge this morning. white flags where american flags are supposed to be. they were in fact made from old glory bleached white. but the question is who switched them out and why? speculation raging today over whether this is some sort of political statement or maybe just a strange art project. the police, however, are concerned with more concrete questions like how did anybody access this highly surveilled location and pull off such a high-risk, high-profile stunt? that said, we can rest assured, we are told that they do not believe this incident was connected in any way to any sort of terror threat. and you can stay with abc news for all the latest developments

on this mystery. thank you for watching abc tonight. tune in to "gma" first thing in the morning. and as always, we're online at abcnews.com 24/7. good night. every day more americans choose abc news. america's number one news source. i've never seen this place so crowded. yeah, ever since marco took over, the food is supposed to be unbelievable. oh, thanks. was that stefania? no. which one is she? amy, you know, maybe we should eat somewhere else. there's plenty of other restaurants where robert's ex-girlfriends don't work. no, no, no, she took my boyfriend. now she can take my order. yeah, but i just don't get -- oh, my g. how is this so good?

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