Transcript for What happened when Otto Warmbier was detained in North Korea: Part 2

Nexgard. The vet's #1 choice. ??? Reporter: A stranger in a strange land, Otto Warmbier is making the most of his north Korean adventure. The only complaint so far, the cuisine. Otto told this participant, this is all so strange. Reporter: Journalist Isaac stone fish interviewed several of Otto's travel mates. This participant remembered thinking to themselves, oh, gosh, he's really out of his league here. Reporter: And out of his league, possibily because this trip is much more than mosaics and military parades. It's a party. Among the stops on Otto's trip itinerary, taedonggang number three brewery. And rakwon beer bar. Home of the 50-cent pint. Young pioneer tours approach to appeal to younger people is very much one of, "Let's go have fun in North Korea, drink some north Korean beer." Reporter: And based on photos on Instagram, it appears the founder of young pioneer tours, gareth Johnson, likes to chug. And on his arm, a version of the north Korean symbol. It's fine for vacationers to throw back a couple, but reportedly those on the trip with Otto say the tour guides were also indulging. A regular pattern, stone fish says. The problems have been with young pioneer is some sort of recklessness, not enough paying attention to the tourists they're supposed to protect. Reporter: Others tourists have said the guides were professional. The hotel where Otto stayed, I've stayed there, too. Though typically reserved for foreign government officials, it's located on an island, isolating most visitors. But as Rowan, a manager at young pioneers, shows in this YouTube video, there is plenty to do. We're going to show you all the facilities and everything this hotel has to offer for all the tourists that come into Pyongyang in North Korea. Let's go. 25 meter lap pool, it's heated. Reporter: The swimming pool, bowling alley -- Two lanes have recently been renovated. Reporter: And a mini mart, to stock up on those travel necessities. Water, more beer, coffee, Korean lollies. Reporter: But conspicuously missing from this video, the fifth floor. In fact, it's kind of missing altogether. We were kind of given full reign of the hotel, except for one floor. The elevator skipped number five. One, two, three, four, six, seven, eight, nine, ten. . So, we were told, don't even try to get to the fifth floor. Reporter: We are told the fifth floor is for staff only. Off-limits to guests. What actually happens there is the source of rumors, most of them unnerving. It's where they keep the surveillance equipment, where they use to bug all of the rooms. It was a floor unlike any other floor in that hotel. So, this is a video of our excursion to the fifth floor. Reporter: Travel blogger Calvin sun didn't want to speculate. He wanted to see it. So, in 2011, he and some friends snuck onto the fifth floor -- Serious fifth floor. Reporter: And videotaped it. What goes on here, nobody knows. The floor you go onto from four to five has paintings. Reporter: It's not artwork but rather propaganda on the wall. "Military first. Powerful nation," reads one. But perhaps the most disturbing is this, featuring a bomb with usa on it. "Revenge hundred times, a thousand times, to American wolves." Calvin and his friends had no trouble on the fifth floor that night, but others might not be so lucky. New year's eve, 2015. Olt toe, he Otto, headed to Kim il-sung square for fireworks. We see this scene in 2016, in a YouTube video. We're here in Kim il-sung square and it is absolutely packed with people. Happy new year from Pyongyang! They were out in this big square. Just seemed like a fun, festive atmosphere. Reporter: On the eye tent rare for the next morning, a chopper tour of Pyongyang. Probably over the same spot eye saw from the air last year. I can't tell exactly how old this helicopter is, but it's working. And later he was posing for pictures at the grand monument. This one posted on Twitter. And these others obtained exclusively by dailymail.com. Look at how the strapping, all-American towering over the local north Korean women, seemingly a fitting finale to his adventure in North Korea. At the airport, me and Otto were the last two through security. And he simply had a tap on the shoulder. Reporter: Danny Gratton was Otto's roomate during the trip. Two guards took him away, and I sort of laughingly said to him, "That's the last we'll ever see of you." And because we got on so well, Otto turned around and just chuckled at me. Reporter: Gratton says that was last time anyone saw Otto. The tour group was told he was sick and needed treatment, so they left without him. The company says they made numerous attempts to get information about Otto, but for nearly three weeks, no word publicly, until the dreaded news breaks. Breaking news overnight. An American college -- He was arrested while perpetrating a hostile act. They are not saying anymore than that. To hear your friend's name on national television and really -- you don't really ever get accustomed to that. Otto Warmbier was charged with hostile acts against the state, which is a kind of catch-all charge that North Korea levels against people who have done anything. Reporter: And what exactly did Otto do? The north Koreans point to this surveillance video. They say that's Otto on that infamous forbidden fifth floor of the yanggakdo hotel, attempting to steal one of those propaganda posters. But the video is so grainy, nobody really knows if it's him. It's unprecedented to do somethingle to a poster with the dear leader on it? It's punishment. Reporter: The following month, he was marched in front of TV cameras and made his so-called confession. I understand the severity of my crime and I have no idea what sort of penalty I may face. The confession that Otto Warmbier gave before the cameras early last year, it seemed scripted for him. I never should have allowed myself to be allured by the United States administration to commit a crime in this country. He admitted to a really bizarre range of things, like belonging to a secret society, stealing this poster on orderers from somebody in a church. It's incredibly clear that it was a performance. Please. I have made the worst mistake of my life. Reporter: For his friends, watching it back home in America, the only thing real were his tears. Another month passed and Otto appeared in a north Korean court. This time, to learn his fate. North Korea runs these kind of sham trials. Yes, it was less than one hour, Otto had no defense, you know, he was guilty before he went into this. Please think of my family. I am the oldest son in my family. Reporter: 21-year-old Otto Warmbier is sentenced to 15 years in prison, hard labor. The adventurous and curious college student who came to North Korea to have fun, throwing snowballs with kids, now in handcuffs, head down.

This transcript has been automatically generated and may not be 100% accurate.