tonight, it starts with flowers and ends with funerals. our journey into the heart of the mexican drug trade, where killers are worshiped and violent cartels enforce their own kind of justice. >> just to be clear, your job involves killing people sometimes. >> america's opioids cooked in a cauldron, expertly smuggled, leaving a river of blood in their wake. >> they're right here on the street. see, there's a cooler, and inside that cooler we're told there is a human head. >> a country in crisis. with bodies piling up and no end in sight. "mexico: march toward hell" will be right back. k.

"mexico: march toward hell" continues. dan harris reporting. >> fentanyl and opioid overdoses making headlines -- >> babies born hooked in a birth fight because -- >> overdoses are on the rise in our community. >> these beautiful flowers in a sun-dappled field in northwest mexico.

are the source of an american catastrophe. >> she injected the boy with heroin -- >> two mothers overdosed on heroin -- >> they found a second overdose victim, a man inside the car with the kids. >> poppy. the raw material for heroin. the workers use sawed-off deodorant cans to collect the gum from the poppy buds. you're getting the gum out of the poppy. >> yeah. >> reporter: here among the armed workers we find a grandmother recently deported from los angeles. she's now petitioning to return. >> do you miss your family? >> really -- yeah. very much. very much. >> reporter: she says she's an uber driver and harvests poppies on the side. obviously you know this because

you lived in the united states, but the heroin epidemic is a huge problem. do you have any concerns about being part of it? >> i need the money only. you know, doing this when i feel very bad. i feel like dirty, you know. but i need money. >> build that wall. build that wall. >> build that wall! build that wall! >> reporter: in the age of trump mexico has become a heated part of the national debate. >> they're bringing drugs. they're bringing crime. they're rapists. >> reporter: but often overlooked in the furor over mexico's role in illegal immigration and the influx of opioids is the fact that america's seemingly bottomless demand for drugs is fueling a crisis inside mexico. the country is on what one expert has described as a march towards hell, gripped by an unprecedented spike in drug and gang violence, even increasingly in places where americans go on

vacation. we decided to see for ourselves, starting with an extraordinary tour of the inner workings of the sinaloa drug cartel, the single largest exporter of heroin to the u.s. the next step after you harvest the poppies is you need to cook the gum into heroin, and that's what we're going to see now. we're driving out into the countryside to find a cook who's allowed us to document his process. two young cooks here suiting up. real-life "breaking bad." >> reporter: this is the first time they've allowed american journalists in to document the entire heroin supply chain. the cartel contracts with a large network of freelance cooks who change up their work sites regularly to avoid authorities. today these young men are in a poorly ventilated abandoned house. >> they don't use fancy

equipment here. two metal pots, some stones and literally a stick to stir it all with. the smell is pretty serious. it's a heavy chemical smell. >> reporter: the main cook says he's 25 years old and has been doing this work since he was 15. so there are a lot of chemicals in this. would you ever inject this into your body? "no, not at all," he says. "it's like a disease that can trap you until you die." you have a sense of how much harm this can do. do you have any misgivings about making this drug since you know how bad it is for people? "the truth is i do," he tells us. on the one hand he wouldn't want his family members to use heroin. on the other he says if you decide to drug yourself that's your problem. >> to be honest, i need to step

away for a second. these fumes are hard. >> reporter: this process will yield a kilo of heroin. the cooks say that will earn them $1,500. by the time it gets to the u.s., they say, it could sell for up to $45,000. and this is the final product after a daylong process of cooking and chemicals. white heroin. >> he's an unusual variety of chef who takes pride in his work but does not recommend you consume his product. if president trump builds a wall along the border with mexico, will it be much harder for this stuff to get into the united states?

"it's not hard for us," he says, "was we have a tunnel to get it from tijuana to the u.s. or by car. any way we can." >> what would shut this business down? is there anything that could stop this industry? his answer, "it's never going to stop." at night the next step in the chain. smuggling the product up into america. we meet another masked young man. this one who learned a bit of english during a brief stint living in california. >> cocaine. a kilo. >> reporter: he's got a briefcase filled with both heroin and cocaine which he offers to us and freely admits to using himself. his associate loads the drugs into a hidden compartment in the door of this car. there's a total of 28 kilos. half heroin, half cocaine, in the car. worth millions of dollars on the street. this is clearly not the first time he's done this. they tell us they'll drive the drugs to the border, then put

them in different cars to drive across. >> who takes the car across the border? is it mexicans or do you find american citizens to do the work? >> american citizens. >> american citizens. how do you find americans to do this? >> i don't know. >> your boss does that. >> yes. >> your boss does it. interesting. >> reporter: the fact that they apparently have americans helping them may help explain why no one here seems too worried about president trump's proposed wall. "we will keep getting things to the other side," he says. "and if we don't, the truth is americans will be the ones to knock over the wall to come to mexico then." this car's final destination -- los angeles. in 2016 the sinaloa cartel took a huge hit. the arrest its leader, joaquin "el chapo" guzman, who goes on

trial in new york in september. but here in this part of mexico the cartel is still essentially in control. we did see the army out on patrol, but this is hostile territory for the government. a place where people regularly worship the patron saint of narco traffickers, where the local cemetery is filled with garish monuments to dead drug lords complete with wi-fi and air-conditioning. on our final night in sinaloa we met with the men who believe they are the true authorities here, the cartel's armed enforcers. so they are pretty eager to show us how well armed they are. see, that's a grenade. with our cameras here they're in full battle gear showing off their weaponry, much of it american made. off to the side the commander gives us some bracing insights into what his job actually entails.

>> just to be clear, your job involves killing people sometimes. "yes," he says. does that take a toll on you psychologically? "the first time it did, but not anymore. i'll never forget the first time." to our surprise he admits the arrest of el chapo did hurt the cartel for a while. it set off a violent power struggle. and now according to this mid-level enforcer it is business as usual. indeed, a desire to demonstrate that fact may explain why the cartel allowed us in to document their operations. it does, however, highlight a bloody catch 22 for the mexican government. they have broken up many of the cartels, but that has only fueled skyrocketing violence with smaller gangs competing to fill the vacuum. next, we witness a grotesque example of this when we head to the legendary tourist destination of acapulco. a bloody war being fought in what used to be a paradise. >> three bodies in a day, it's like business as usual.

>> stay with us. ♪ with roomba from irobot, clean floors can be part of your family's everyday routine. roomba's two unique multi-surface brushes grab and remove everything from fine dust to large debris and even pet hair. and roomba uses a patented dirt detect™ system that attacks dirt in high-traffic areas of your home. so you can come home to clean floors everyday. you and roomba from irobot. better together. hais not always easy. severe plaque psoriasis it's a long-distance run and you have the determination to keep going. humira has a proven track record of being prescribed for over ten years. it's the #1 prescribed biologic by dermatologists. more than 250,000 patients have chosen humira to fight their psoriasis. and they're not backing down. for most patients clearer skin is the proof.

humira can lower your ability to fight infections, including tuberculosis. serious, sometimes fatal infections and cancers, including lymphoma have happened, as have blood, liver and nervous system problems. serious allergic reactions and new or worsening heart failure. before treatment get tested for tb. tell your doctor if you've been to areas where certain fungal infections are common and if you've had tb, hepatitis b, are prone to infections, or have flu-like symptoms or sores. don't start humira if you have an infection. join over 250,000 people who have chosen humira. ask your dermatologist about humira & go. new digestive advantage now has probiotics that add good good bacteria to your body... and prebiotics that feed the bacteria you already have. together, they support your digestive health. one pill, two ways to help you... stay strong.

our 3 contestants are all at the big ikea table. who's going to be tonight's winning chef? contestant #1, impressive knife skills. but contestant #2 fights back by using fresh parsley. and, contestant #3 adds a touch of sweetness. sweetie, come eat outside. but it's to hot out there! perfect! make room for the judge! what's your dream? at ikea, we help you live it. make the dream yours. ♪ ♪ ♪ raindrops on roses and whiskers on kittens ♪ ♪ bright copper kettles and warm woolen mittens ♪

♪ brown paper packages tied up with strings ♪ ♪ these are a few of my favorite things ♪ ♪ ♪ i thought after sandy hook, where 20 six and seven year olds were slain, this would never happen again. it has happened more than 200 times in 5 years. dianne feinstein and a new generation are leading the fight to pass a new assault weapons ban. say no to the nra and yes to common-sense gun laws. california values senator dianne feinstein

>> announcer: >> announcer: "mexico: march towards hell" continues. late night in the legendary mexican resort city of acapulco, and we are arriving at a crime scene in the middle of a residential neighborhood. so right here on the street you'll see there's a cooler, and inside that cooler we're told is a human head. th the norm here in this storied

city. and indeed across mexico, which is witnessing the highest levels of violence ever recorded. cops ambushed. political candidates assassinated. even popular vacation spots for americans such as cancun seeing a spike in murders. much of it driven by gangs. fighting for a slice of america's lucrative market for heroin. we set off on a four-day journey into acapulco's underworld, one that would get darker than anything we could have imagined. we just pulled into acapulco. that name, acapulco, seemed to be synonymous with luxury. ♪ let's fly away this is the city that frank sinatra sang about. ♪ beat the birds down to acapulco bay ♪ >> it was the playground of

people like elizabeth taylor and the kennedys. now it's one of the most violent cities in all of mexico and in fact the world. there has long been drug crime in acapulco, but for years it was controlled by one powerful cartel. when the government killed or captured the cartel's top leaders, however, smaller gangs started fighting for control. we're a little over 24 hours into our stay, and already our first murder. good to see them working through here. the body was found in the woods on the outskirts of acapulco, a convenient place to dump casualties of the drug war. then a sight that will become all too common for us over the next few days. collecting the dead. ivan rivera lopez has been working for the morgue for five years. is this the first murder victim whose body you've collected today? no, he says, he's already collected another body. do you think at a certain point you become numb to the violence?

"no one is immune," he says. "i'm at risk as much as everyone else." hours later another crime scene. a man who was evidently tortured and dumped on the street as a message to rivals. i've covered wars all over the planet, and this kind of savagery right out in the open is even to me shocking. it looks like he was thrown from an open car. then a familiar face. it's ivan, the morgue worker. this is his third murder of the day. i wonder, for you, this to me is just incredibly grotesque. is this shocking to you? "yes," he says. "because this is a human life." three bodies in a day is business as usual. not surprising. okay. ivan, gracias. just looking at this view, this

place is beyond beautiful. how has it become so violent? >> reporter: the second highest ranking law enforcement official in the state. insists the tourist areas of acapulco are safe. when you tell me what happened with the violence in acapulco, the violence in acapulco is not on the touristic city. >> a lot of people advised us when we came here, look, be careful, don't take a taxi. are you saying they were being overly cautious? >> yes. of course. >> so just a few hours after the vice attorney general told us there's very little crime in the tourist areas, there's been a murder here on one of the main avenues in the city, which is not far from the beach.

>> reporter: the victim, a 54-year-old family man who owned a small food stand in this mall. oh, man. a family member. so sad. apparently, he was being extorted and refused to pay. so he was shot six times in the face. the responding officers don't seem nearly as gung ho about crime prevention as the vice attorney general. do you think they'll ever catch him? >> it's really difficult because he just boom-boom and run. >> people run all the time. the next day -- >> we've come to a funeral and found not only a whole group of mourners but also a whole group of police officers. it's not uncommon for the gangs to come up and shoot up the funeral. the victim's son agreed to be interviewed as long as we did

not disclose his identity for fear of being the next target. do you have any hope that they'll catch the people who did this to your father? "we know how this works," he says. "the police when they return the body they close the case. there's no investigation." in this city where in the end we witnessed six homicide scenes in four days, and that doesn't even include the ones we were told were too dangerous to film. it was a trip to the morgue that gave us the clearest sense of how much local authorities are struggling to keep up. we saw unclaimed, unidentified bodies stacked like cordwood, badly decomposing in poorly functioning freezers. so this is an unknown male who came in here almost two years ago. august of 2016. so what's been happening for two years with this body? the morgue director says his team has been scrambling to clear out the backlog. at morgues across mexico they're experiencing a relentless tide of blood that nobody expects to abate as long as americans

continue to demand the products that the cartels provide. it's so bad here that the morgue director is now shipping the unclaimed, unidentified bodies to a facility in the state capital to relieve the burden. >> this is just an incredible thing to look at. these were people. you know, with inner lives just as vivid as our own. now they just have to stack them on top of each other and put them in a truck and take them away. and so on a hilltop outside of acapulco 30 nameless people are given a temporary resting place in these large concrete slabs. in an ominous sign they are planning to build a dozen more of these structures. monuments to a cycle of drug

consumption and drug violence on both sides of the border. a war with no end in sight. >> announcer: abc news "nightline," sponsored by taltz. but does psoriasis ever get in the way? embrace the chance of 100% clear skin with taltz. up to 90% of those with moderate to severe psoriasis had a significant improvement of their psoriasis plaques. most people were still clearer after one year. with taltz, 4 out of 10 even achieved completely clear skin. don't use if you're allergic to taltz. before starting, you should be checked for tuberculosis. taltz may increase risk of infections and lower your ability to fight them. tell your doctor if you have an infection, symptoms, or received a vaccine or plan to. inflammatory bowel disease can happen with taltz, including worsening of symptoms. serious allergic reactions can occur. ready for a chance at 100% clear skin? ask your doctor about taltz. with roomba from irobot, your family can expect clean floors everyday.

two unique multi-surface brushes and power-lifting suction pick up dirt, large debris and even pet hair. so your floors are always clean. you and roomba from irobot. better together. ( ♪ ) it's the details that make the difference. only botox® cosmetic is fda approved to temporarily make frown lines, crow's feet and forehead lines look better. it's a quick 10 minute treatment given by a doctor to reduce those lines. ask your doctor about botox® cosmetic by name. the effects of botox® cosmetic, may spread hours to weeks after injection, causing serious symptoms. alert your doctor right away as difficulty swallowing, speaking, breathing, eye problems, or muscle weakness can be a sign of a life-threatening condition. do not receive botox® cosmetic if you have a skin infection. side effects may include allergic reactions, injection site pain, headache, eyelid and eyebrow drooping and eyelid swelling. tell your doctor about your medical history, muscle or nerve conditions, and medications including botulinum toxins

as these may increase the risk of serious side effects. the details make a difference. the man makes them matter. see real results at botoxcosmetic.com/men.

the man makes them matter. it's "watch what you want on the fastest internet" streaming. it's "live sports so you never miss a goal" streaming. it's "dvr shows because you'll never know when you'll need it" streaming. it's streaming from xfinity that makes your life... simple. easy. awesome. get started with xfinity internet for $40 a month for 2 full years when you sign up for tv. plus, get 3x the speed of at&t and directv. click, call or visit a store today. that violent crime went up 18% in san francisco. in la, mayor antonio villaraigosa put more police on the streets and cut violent crime in half. california's police chiefs trust antonio for governor.

one final note from our one final note from our studios in new york, where we have been reflecting as we prepared tonight's report on those images from the poppy fields, that maddening combination of beauty and lethality. as we say good night, i want to thank the many people who worked so hard and risked so much to bring you this important story. i also want to thank you for watching "nightline" tonight. good night.