tonight on "20/20" -- what some might call a real life "game of thrones." a ruling family as complex as any fiction. >> we go to pyongyang where the unpredictable and dreaded dictator kim jong-un keeps his finger on the nuclear button. >> this former bodyguard says his explosive temper was there from childhood. and he now runs the most dangerous country in the modern world, he says, with nuclear missiles aimed at the u.s. if you're a family rival, you may fear for your life -- like his older brother. >> i was hopeful the that kim jong-un could replace him. >> in an airport in malaysia, that brother murdered in plain sight. >> it was an incredibly elaborate plot. took months, maybe even years to

set up. >> a nerve agent that kills in minutes. >> vx, the nerve agent, is one of the most dangerous substances out there. >> was the kid brother who president trump calls little rocket man responsible? >> you knew this was kim jong-un's order. >> only one person who can make that order and that's kim jong-un. >> tonight, eye-opening access to a story most americans have never heard. >> just waving out to the crowd. >> our "20/20" investigation with bob woodruff, one of the few journalists ever to visit the hermit kingdom. three continents in three months. >> what we're seeing is, there he is walking in to the airport. >> those still in danger. >> my father has been killed a few days ago. >> those who fear for the families that this "game of thrones" could kill. >> the entire family, they're all gathered up and all killed. >> a dynasty, a murder, and a shadowy kingdom. >> i'm david muir.

>> i'm elizabeth vargas. and this is "20/20." >> you could not have had a crazier story. it was like a movie, it really was. >> it was planned. it was executed in a professional way. and it was done exactly how they wanted to do it. >> it's embarrassing to have a murder of this magnitude take place in your international airport. >> the way he died was the most gruesome, painful way that one could die. >> reporter: kuala lumpur international. the largest and busiest airport in malaysia. somewhere in this sea of humanity is a man going by the name kim chol. he supposed to be departing for macau. what he doesn't realize is he's about to die. watch as airport surveillance

captures the middle-aged man casually dressed in a t-shirt and blazer, checking his flight information. from a different angle, you can see he is now under attack. one of two alleged assassins approaches from behind to smear something on the victim's face. the dazed man seeks medical assistance inside the terminal but time is running out. he will be dead before he ever reaches the hospital. >> he's, like, a chubby middle-aged man walking through that airport. and then suddenly, two young women just grab him by the face and spread some type of chemical on him. >> indeed. it was called vx, a nerve agent. >> reporter: one of the alleged assassins departs the terminal via taxi. she's wearing a shirt that says "l.o.l." >> it was very specifically targeted at just getting this one man. >> reporter: why target him? because he's actually north korean royalty. he's also traveling with a fake passport.

his real name? kim jong nam, half-brother to the most enigmatic leader in the world, kim jong-un. >> the alarming claim from north korea. >> he has responded in kind with threats of new missile tests. >> we begin a horrific cycle of violence. >> reporter: "20/20"'s three-month investigation into the ties between this unlikely pairing took us from malaysia to tokyo, to switzerland, to macau. we uncovered what appears to be a cain and abel-like tale that reveals hidden insights into the mysterious dictator. and the lifelong rivalry with the brother once considered to be the rightful heir to the north korean throne. >> some people believe that kim jong-un perceived him as a rival. >> reporter: think of it as east asia's version of "game of thrones," where the storyline is always about power and who has it and who wants it. the kim dynasty has ruled north korea with an iron fist for 70 years, remaining isolated and

secretive by design, according to former cia analyst sue mi terry. >> how much do the people in north korea know about their leaders? >> very little about their personal lives, or how they grew up, and what they do. nothing that's beyond propaganda. >> reporter: according to north korean legend, the kim family sprang from here, majestic mt. paektu, that straddles north korea and china. kim jong-un's grandfather and father are often depicted standing on top of the mountain. >> they say he was born here. >> reporter: it's beautiful for sure as i learned when i climbed to the top of the chinese side last year. the myth may be legendary, but the reality, touristy. no leaders, just followers as we made our way to the top. >> china. >> reporter: the sacred family tree of the kim dynasty starts with kim il-sung, north korea's

founder. their "great leader." his offspring, kim jong-il. esteemed as the "dear leader," known for his bizarre haircut and penchant for jumpsuits and platform shoes. but it is the third generation of the bloodline where three young brothers first appear. and it is the oldest, kim jong-nam, who was destined to one day lead. finding interview subjects to discuss the early years of kim jong-nam is easier said than done. because before they can talk, they have to escape. >> this is downtown toronto. we've found one defector. >> reporter: his name is lee young-guk and for 11 years, he was kim jong-il's bodyguard. how did you become a bodyguard for kim jong-il? >> translator: based on personality, character, morals, and stamina. i was selected out of 14,000 people. it was a 14,000 to 1 competition.

>> reporter: lee was able to watch as the oldest son, kim jong-nam, was groomed as a potential successor, seen here dressed in military clothes as a child. did kim jong-il have a good relationship with kim jong-nam, his eldest son? >> translator: kim jong-il raised him and took him around himself. kim jong-nam had a good personality. he was chubby with a friendly personality, and was very humane. >> reporter: for someone who routinely and publically displayed a hatred of the u.s. and its capitalist ways, kim jong-il had a bizarre fixation with western culture, especially its movies. he loved everything from "rambo" to "dumbo." and when it came to the educations of his children, kim jong-il shipped them far off from their backward and isolated homeland to switzerland.

jong-nam ended up at this international school in geneva, where the western education had a profound influence on him. >> we understood that kim jong-nam, as a young man, was more reform minded, pro-western, liked western things. and thought north korea was on a wrong path. >> reporter: it was all just a matter of time, experts said, before kim jong-nam would one day be the natural heir to the family dynasty. but then he blew it. in 2001, kim jong-nam was caught at an airport in tokyo, trying to enter with a fake passport to visit tokyo disneyland. the name he used, pang xiong, which means "fat bear" in mandarin. ♪ makes no difference who you are ♪ >> reporter: apparently it made a big difference to the north korean regime. >> japan is one of the enemy countries of north korea, so to be caught in japan, trying to enter japan with a fake passport, this was a huge

embarrassment to the regime. >> reporter: the "fat bear" quickly fell out of favor and was sent packing to macau where he remained a definite but distant threat. >> he understood that he posed a threat to kim jong-un. so he feared for his safety, he feared for his life, so he didn't want to go back to north korea. >> reporter: coming up -- kim jong-un at the crossroads. how eric clapton inadvertently helps set the stage for the leader of north korea. when we return.

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>> reporter: by now, north korean dictator kim jong-un is a familiar boogeyman to the u.s. >> north korea testing a powerful missile. >> reporter: mocked by president trump. >> little rocket man. >> reporter: even lampooned in the seth rogan-directed comedy "the interview." >> you know what's more destructive than a nuclear bomb? words. they hate us. >> reporter: but the story most americans don't know is how kim jong-un beat out two older brothers to win the north korean "game of thrones." but to understand the tale of the brothers, you first have to understand the tale of their mothers. >> kim jong-nam's mother was the first and real wife of kim jong-il. north koreans differentiate the real wife as a first wife, and that anybody that comes after is just kind of a mistress.

>> reporter: and in fact, it is a mistress who gives birth to the current north korean leader, kim jong-un, as well as another son named jong-chol. according to that bodyguard, life for the illegitimate kim jong-un is one of silence and shame. >> translator: his existence was a secret. kim jong-il built hidden houses for his concubines. it was similar to house arrest. >> reporter: the bodyguard says that isolation left its mark on the young boy. >> translator: he was stressed and had no one to play with his own age. there were only adults, who educated and played with him. >> reporter: was he a young boy who felt everything was coming his way? >> translator: he was quick-tempered. he doesn't care about what others think. he doesn't feel sorry for other people. he does whatever he wants. >> reporter: lee says the lonely child did have a special treat

which was rare visits to the kim family's monumental vacation resort in the town of wonsan, restricted to all outsiders. it has its own landing strip, private beach, even its own soccer stadium. >> translator: there is no one in this world who has felt as much pleasure as the kim dynasty. >> reporter: just like his more legitimate half-brother, kim jong-un is shipped off to switzerland for his education ending up here in 1996 in the stately swiss capital of bern. kim lives in this unassuming apartment complex under the watchful eye of his mom's sister and attends this international school. it's hard to find anybody that met him. to get the inside scoop on kim's unlikely life in switzerland, we caught up in tokyo with "washington post" bureau chief anna fifield. fifield landed an exclusive interview with kim's caretaker aunt, who defected to the u.s., now running a dry cleaning store and unwilling to have her face

shown. >> he wasn't very interested in doing his lessons. he had kids over to play, he went in the, you know, family minivan off to the swimming pool and things. so, it sounds like he did have a relatively normal life. >> reporter: still, inside that modest apartment, classmates find signs that there's something special about their asian friend. >> he had all of the latest technology, which at the time in the '90s, was a minidisc player. he also had access to a lot of films before they were released in the cinema, like jackie chan movies. jean-claude van damme was another favorite. and he also had these very fancy nike air shoes that cost like $200, an extraordinary amount of money at the time. >> reporter: those expensive

shoes indicate that the 12-year-old korean is passionate about an american sport basketball. he is especially obsessed with michael jordan's chicago bulls. >> his aunt told me it was kim jong-un's mother encouraged him to take up basketball because there is this belief among korean mothers that if you play basketball you will grow up to be tall. >> reporter: although he only grew to be 5 1/2 feet tall, every single day after school, young kim would race to the basketball court to play with the local kids. >> he would practice and practice and practice. what he didn't have in natural talent he made up in determination. and he was seen wearing a chicago bulls jersey all the time. >> reporter: so, just how did this basketball-crazed kid end up as the supreme leader of north korea? well, as you'll recall, that older half-brother, kim jong-nam, was apparently taken out of the running after his ill-advised attempt to sneak into disneyland. his humiliating fall from grace leaves a huge opening on the other side of the family tree for the sons of the mistress.

>> kim jong-un's mother, i hear, was a very ambitious woman, and that once kim jong-nam got caught in this very embarrassing situation, sneaking into japan, that she capitalized on that and used that to promote her own children. >> reporter: the logical next son in line is kim jong-un's older brother jong-chol. but he would be the next domino to fall. he, too, was undone by a fixation with western culture. namely, the music of eric clapton. ♪ he embarrassed the regime after he was repeatedly caught sneaking into clapton concerts. here he is in 2015 being snuck into a concert in london by a north korean diplomat. >> he doesn't have the right temperament, the characteristics. that's what his father thought. >> reporter: that leaves the path clear for the youngest son, kim jong-un, the only one not to publicly embarrass his father. and those aggressive qualities he displayed as a child now

impress kim jong-il. >> he had a little bit of a tough streak in him, and that's what his father liked, that he was strong, that he acted like a leader. >> reporter: and soon enough it's clear for the world to see kim jong-un is positioned to be the future ruler of north korea. when we return, kim's obsession with the chicago bulls pays dividends. an unlikely alliance with the one american who got close enough to call him "friend." >> tells you a lot about our friendship here. >> reporter: and what could be the last straw for that errant half-brother. what he does that makes him kim's sworn enemy. stay with us.

>> reporter: december, 2011. north korea says good-bye to

the dear leader kim jong-il, as 27-year-old kim jong-un, one of the pallbearers at his father's funeral, assumes the leadership of his country. but he is as much a mystery to north koreans as he is to the west, who hope he will herald change. >> i don't think we know too much about this person that's the leader of north korea right now. >> reporter: but one thing is clear. kim takes a very different public path than his reclusive and eccentric father, patterning himself instead on his legendary grandfather kim il-sung. >> it is no accident that kim jong-un has put on all this weight, and has got the same haircut, and very often wears the same clothes as his grandfather. >> and smiles the same. >> smiles the same, everything is very obviously designed to remind north koreans that, you know, not only does he have this divine right to be the leader of north korea, but that he can make life better for north koreans. >> there he is. waving out to the crowd.

>> reporter: during my reporting trips to north korea, i was never allowed to get close to the enigmatic leader. have to stay within five feet of each other? here, when he suddenly showed up at this museum opening and caused a frenzy among the press, we didn't get a chance to ask any questions. it turns out, one outsider with firsthand knowledge and personal contact with the north korean leader is not a diplomat or an american spy. it's this man. the only american known to have become close to kim after he assumed power. the flamboyant former nba star and chicago bull dennis rodman. his latest attempt to get into north korea was sponsored by a company called potcoin. rodman made international headlines when he visited north korea in 2013 along with a vice tv crew, at the invitation of the chicago bulls-obsessed leader.

at a goodwill basketball game, rodman was seen talking intently with kim. later, rodman and his entourage got the surprise of their lives. an invitation to party with the mystery man. so since you had the chance to, i mean, just to shake his hand and talk to him, how is his english? did you speak english to him? >> he said, hi. he said, okay now. but, but he has no, no english at all. >> reporter: so it looks, i mean it looks like you guys are talking here but this just, he's just speaking through his interpreter. >> no his, so every time we -- you see us talk like this, we're talking about basketball and he always asked me, said, "dude, i would love to go to new york, but i can't." he says stuff like that. >> reporter: what was he like? did he seem serious? >> he's always smiling, man. he's all, he's always smiling. especially when we -- you're around his, his comfort zone. >> reporter: in terms of basketball, did he play basketball at all? >> he said dennis, let's play horse. so we go to the free-throw line. he hits that. i said, all right. i missed the free throw, of course.

and then next thing you know, he goes on other side of the corner over there, and he hits. i said dude, this guy can shoot. >> reporter: rodman has visited kim three times now. and was one of the privileged few allowed to visit that luxury resort that kim used to visit as a child. he rode horses with the dictator, met his wife and baby daughter, and partied late into the night. >> it was, like, 70 people at this big round table, man, like, wow, i mean. and everybody had their turn with, they had a shot of vodka. and then they'd try to say karaoke. it's 70 people trying to sing karaoke. >> reporter: how is he as a singer? >> he's pretty good. >> reporter: what did he sing? >> he was singing frank sinatra, "my way." >> yeah, he had this girl band. like 14 girls. they travel with him everywhere, to play his music. >> reporter: so he had the lyrics and a screen. he was reading it in english. >> he would do, he was singing it in, in all korean. >> reporter: rodman makes no apologies for his embrace of a dictator who lives the high life while so many of his countrymen

suffer in misery. >> it's a friendship hug. you rarely see this in the world. even with his grandfather and father. you don't see the leaders do this, especially an african-american. you never see this in north korea. >> reporter: but it's a country with a lot of starvation, now, too, though. is that okay? >> well, you know, a lot of, a lot of people in the world are starving. even though they say he's a bad man but he, to me, he's not a bad man. i didn't see that part. >> reporter: rodman may not think kim's bad, but there's someone else who had serious concerns about him. his errant and disgraced half-brother, kim jong-nam. he and his family are living in the tiny chinese territory of macau, known as a mecca of gambling and glitz. >> the city provided security. many people i talked to in macau believed that kim jong-nam and his family were in macau under beijing's protection. >> reporter: but even in exile, kim jong-nam still worries about the fate of the north korean people under the rule of his

half-brother. and perhaps unwisely, he begins speaking out. in tokyo, i met one of the few he confided to -- japanese journalist yoji gomi. how did you get a chance to meet kim jong-nam? >> i came across him at beijing airport. i am very surprised, i start interviewed him, a lot of questions at the time. >> reporter: gomi landed a rare interview with the elusive kim at a macau restaurant. >> translator: i learned a lesson, not to do reckless and immature acts. i made a big mistake so it somehow aroused father's anger. >> reporter: but perhaps the most reckless of his acts was criticizing his brother's rule. in a series of published e-mail exchanges with gomi, kim wrote, "the kim jong-un regime will not last long. without reforms, north korea will collapse, and when such changes take place, the regime will collapse." >> kim jong-nam said to me,

north korea should be reformed and make north korean people more rich and happier. it's a message to kim jong-un. >> reporter: but do those comments make kim jong-nam a marked man? coming up, the north korean dictator goes on a killing spree. and not even his own family members are safe from his wanton cruelty. >> translator: nobody did it this brutally, this barbarically. kim jong-un used anti-aircraft machine guns. you cannot even bury a dead body, because there is no dead body, it has just been obliterated.

>> reporter: you haven't seen a parade until you've been to north korea. every year we try to spot anything new. i have seen firsthand how kim jong-un plays the part of the smiling, benevolent leader. the last time i was here, that was his father doing the exact same thing. but in 2013, that beaming man turned out to be a wolf in sheep's clothing when he did something that appalled the world. >> we head to north korea. >> the news of the execution has stunned this region of the world. >> reporter: in front of a meeting of the north korean

politburo, he publicly arrested his own uncle, jang song thaek, a powerful figure known for being reform-minded and close to china. accused of corruption, jang was executed, reportedly blown to pieces by an anti-aircraft gun in public. >> i was shocked that kim jong-un got rid of his uncle so brutally, so publically. so that ruthlessness shocked me. >> reporter: and the killing of his uncle was just the start. in 2015 it was revealed that kim was unhappy with the head of the country's armed forces for complaining, talking back, and the greatest sin of all, falling asleep during a meeting. >> the country's top defense official has reportedly been executed because he fell asleep during a meeting. >> reporter: kim reportedly had him publically executed, again by a favored method, blasted to kingdom come with an anti-aircraft gun.

why do you think that kim jong-un is so much more violent and in some ways unpredictable compared to his father? >> i think it's a combination of his own character, his own temperament, and the environment because he is less legitimate so i think he does have this deep insecurity in terms of being able to rule and consolidate power. >> reporter: the gangster-style korean strongman embracing his inner gunslinger for the cameras. off-camera, launching a ruthless campaign of terror, killing anyone suspected of being disloyal. remember those pallbearers alongside kim jong-un at his father's funeral? one by one, these former elites have vanished from public life, retired, missing, or executed. this man, ri jong ho, was one of the most important officials in north korea, running the office that raised foreign cash for the kim family. he fled to the west with his wife and two children.

he says he was terrified that they too would fall victim to kim's wholesale slaughter of the elite. >> translator: if you get caught, you and your entire family can get executed simultaneously. so people don't even think to do anything because they're too scared. >> how else can i prevail against so many enemies? >> reporter: even hollywood paid a price when it mocked the north korean leader in the movie "the interview." kim was not amused. according to u.s. intelligence, he ordered a hack of sony's computers, and threatened terror attacks on theaters that dared to show the film. >> one of this largest theater chains says it is pulling the plug on "the interview." this is hitting sony in the wallet. >> he doesn't have great a sense of humor in terms of people making fun of him. >> reporter: it doesn't take much to tick off the dictator. as a young american student named otto warmbier discovered. >> breaking new overnight.

an american college student -- >> reporter: "20/20" reported extensively on the case last june, devoting an entire program to warmbier's plight. he was arrested while perpetrating a hostile act. they are not saying any more than that. accused of stealing a propaganda poster. >> i never should have allowed myself to be allured by the united states administration to commit a crime in this country. >> reporter: sentenced to 15 years of hard labor, but after a year, the north koreans sent him home. >> they did not do this out of the kindness of their hearts. north korea doesn't do anything out of the kindness of their hearts. >> reporter: it turns out the 22-year-old had suffered a brain injury and fallen into a coma while imprisoned in north korea. six days after he got home -- >> their son who has returned from north korea with severe brain damage has now died. >> reporter: meanwhile, defectors say the dictator tightens the screws on anyone associated with his big brother.

tell me the people who were related somehow with kim jong-nam. >> translator: anyone around kim jong-nam who helped him, anyone who had even a few meals with him, anyone who had a relationship with him at all was executed. >> reporter: back in macau, where he was living a life of elegant exile with his family, kim jong-nam knew he was now in extreme danger from his murderous half-brother. >> according to some people i talked to in macau, he did fear for his life. he knew that his brother was after him. >> reporter: then it is february 13th, 2017. and here's kim, about to walk right into the arms of his alleged assassins. when we come back, a termination in terminal two. the surprising backstory of the suspected murderous millennials. >> they killed him with their hands. >> they tricked them into committing a murder. >> reporter: what does a tv show prank have to do with it? the investigation into the murder of the dictator's

brother, when "20/20" continues.

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correspondent doug clark dug into the case for "gq" magazine. he points out kim entering the terminal, traveling light, except for a lot of cash. >> there was $120,000 wrapped in very nice, neat bricks in his backpack. and there is some speculation that he came to malaysia to meet with foreign intelligence services. >> reporter: he studies the departure board, unaware he is about to miss the last flight of his life, oblivious to the plot later exposed by malaysian authorities, a death squad of north korean spies and two young women recruited to carry out the killing. >> everyone's already in position. they've been following him for hours. and he has no idea what's coming. >> reporter: abc news consultant and former fbi agent brad garrett says it is a brazen public hit. >> you have the cameras, you have cops, and you have the public to tell you what just happened. so it is an extremely risky thing to do.

>> it was an incredibly elaborate plot. it took months, maybe even years to set up. >> reporter: the story, as malaysian police and prosecutors later reveal it, involves 28-year-old doan thi huong, from vietnam, and 25-year-old siti aisyah, from indonesia. weeks before the hit, clark says, siti is recruited outside this kuala lumpur nightclub by a man who appears briefly in a video she later posted on facebook. clark says the man calls himself "james." he and his colleagues claim to be producers auditioning the women for a hidden-camera tv show. >> sort of like "america's funniest home videos" or something similar, in which they were told that they would be filmed while putting various substances on the faces of strangers. clark says the women did not know each other. he says the producers keep them separate as they rehearse the in-your-face prank in high-end malls and hotels around kuala lumpur and elsewhere.

>> they even took her to the airport, and they had her do dry runs there. >> reporter: the money is good, at least $100 per prank. but there is no tv show. authorities say the producers are north korean agents with murder in mind. the day of the final act, a security camera captures siti in a coffee shop, seemingly without a care in the world, accepting cash from a man with a selfie stick, ready to pull off the final prank. so he's walking through this airport. and then, when he comes up to the kiosk to check in, he's flanked. >> he is. >> reporter: by two women, one on each side, right and left. >> siti aisyah, the indonesian woman who struck first, wiped her hands across his face, stepped back. and then the second woman, the vietnamese woman, immediately wiped her hands across his face as well. >> reporter: the dirty work takes just seconds. authorities say the women smear kim's face with something

provided by the north korean agents. this time, the substance is not harmless. it is vx, one of the deadliest nerve agents known to man. >> and if it's not counteracted almost immediately, you are going to die within a few minutes. >> reporter: one theory is each woman was provided with one half of a special formulation of the poison that only became deadly when combined. all it would take is a single drop. >> and they wiped it across his eyes, his nose, his mouth to get it into his system and then used potentially a second person with >> reporter: as the last minutes of his life tick away, kim approaches airport workers at an information desk. he is concerned enough to rudely interrupt a conversation to get their attention. >> no one seems to really understand the gravity of the moment. the poison is seeping into his body. >> reporter: clark points out this man at the edge of the frame on the security camera. he says it's one of the north korean spies, still

tailing kim. >> the north koreans made sure that they had eyes on him every second. >> reporter: speaking with police, kim gestures to his face. >> and reports of this moment say that he wasn't really making much sense anymore. he was having trouble sort of holding a coherent conversation. >> reporter: they reportedly later say they notice a strange smell. you can see them take a step back. they escort kim to the airport medical clinic. by this time, the poison is already taking effect, causing every muscle to spasm, which explains that suddenly stiff walk. >> and already his legs are starting to stiffen. he's got a little duck waddle going. this isn't sort of that healthy man we saw just moments ago. >> reporter: again, clark points out a man with a roller bag and a strange interest in kim. >> you can see him just sort of strolling very, very casually. he's going to take a quick glance, and then he's going to keep going. >> reporter: he says it's another agent making sure the poison is doing its work, which

it is. minutes later, kim dies in an ambulance. >> those spies immediately, after the hit, went to passport control, cleared passport control before the malaysian authorities had any idea what was going on, got on their flights and escaped the country. >> reporter: as for the two women, after smearing kim's face, they had simply walked away. they did not run. they walk straight into the bathroom to wash their hands. >> malaysian prosecutors have said that this is evidence that the women knew what they were doing. the women's defense is that they had been told by their north korean handlers that they should wash this substance off afterwards. >> reporter: the women, who had made no attempt to hide their faces from airport security cameras, are arrested within two days. six weeks later, malaysia returns kim's body to north korea. about the same time i, too, was returning to north korea and

when my flight landed, we were met by an ambulance. passengers say workers loaded it with a casket from the cargo hold, raising the chilling possibility that we had unknowingly accompanied kim jong-nam on his final journey home to the land of his ancestors. a north korean official did not want to discuss the killing. there was this assassination in malaysia. about kim jong-un's half brother. did north korea have anything to do with that? >> translator: you're bringing things up like malaysia. i don't know why you're acting like this. >> reporter: the north koreans continue to deny having a hand in the airport assassination or even that the victim was indeed kim jong-nam. back in kuala lumpur, the trial of the female assassins, who pled not guilty, got started this summer. if convicted, they face execution by hanging. still ahead, kim jong-nam is gone, but some still place hope

in a surviving branch of the family tree. this mysterious young man appearing in a video online. >> i'm currently with my mother and sister. >> reporter: the hidden legacy of kim jong-nam, a next generation, if he can stay alive. >> there have been rumors in the intelligence communities that a hit is out on him as well. amer. noy my hours are not ruling out the possibility of another north korean missile

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>> reporter: just a couple of months ago, surveillance cameras rolling in the heavily armed demilitarized zone captured video that stunned the world -- a lone north korean soldier, risking his own life, in a dramatic attempt to defect to the south. watch as he speeds along a road, then loses control of his truck. hopelessly stuck in a ditch, and with fellow north korean soldiers in hot pursuit, the only option, run. in a hail of bullets, the desperate soldier crosses to the other side. but he's badly shot, his life in immediate danger. "20/20" has obtained video of the rescue mission and an interview with the surgeon who saved the defector's life. >> he was transferred here from dmz area.

>> reporter: he probably would have died if was not rescued instantly. >> yes, that's right. >> reporter: as authorities sort everything out, experts say there are clear signs that life is getting worse in north korea under the rule of kim jong-un. >> my name is kim han-sol, from north korea, part of the kim family. >> reporter: but could this young man, the son of the murdered kim jong-nam, be the face of hope for the north? >> reporter: in this video, released not long after his father's murder, he says he's safe. >> my father has been killed a few days ago. i'm currently with my mother and my sister. >> reporter: but for how long? intelligence sources tell us he's now the target of death squads, dispatched by his ruthless uncle, forced deep into hiding under chinese government protection. >> kim han-sol obviously also poses a threat to kim jong-un, just by bloodline. so i really hope that he's in safe hands.

>> reporter: today, there are many koreans hoping that the living legacy of kim jong-nam might one day come home to claim his place as the head of the paektu family dynasty. >> we hope this gets better soon. >> incredible reporting tonight. that is "20/20." i'm david muir. >> i'm elizabeth vargas. for all of us here at "20/20" and abc news have a great night and a great weekend. breaking news, a major fire keeping thousands inside