Gangnam B-Side Episode 1:
The episode kicks off with a high-stakes drug raid at a nightclub in Gangnam. Captain Kang Dong-woo and his team infiltrate the scene, despite the Chief trying to stop him. After the arrests, the Chief tries to lure Dong-woo away, but he pushes forward, heading to the basement where he uncovers Detective Jang-ho, caught red-handed packing drugs.
During questioning, Jang-ho insists he’s just the middleman, revealing that nearly everyone in Major Crimes is involved in the racket. His confession leads to the Chief’s arrest, and he warns Dong-woo that he’ll bring him down.
Fast forward three years, and a low-level drug dealer, Lemon, is supplying drugs to VIPs at a club. One of the escorts, Jenny, notices a text from a “Jjuni Boy” warning a VIP to not lose her or they’ll all die. Panicked, Jenny sobers up and calls her friend Jung-hwa to flee. She hides a phone in the club’s restroom and manages to escape.
Elsewhere, a thug beats up Jung-hwa, searching for a video that Jenny has, not realizing she’s already gone. He alerts the club bouncers to find Jenny. Meanwhile, another club’s bouncer, Yoon Gil-ho, helps a drugged-up escort and beats up her dealer, warning him not to deal to his girls. Gil-ho then tries reaching out to both Jenny and Jung-hwa.
Jenny, hiding in an old arcade, refuses to take Gil-ho’s calls while desperately trying to contact Jung-hwa. When Gil-ho eventually finds her, he questions whether she’s involved with Noh Joon-seo, but she remains tight-lipped, too scared for her friend. He promises to find Jung-hwa.
Meanwhile, Dong-woo has retreated to the countryside, where he’s dealing with a DUI involving the mayor’s nephew. The boy tries to bribe him when drugs are found in his car, but Dong-woo resists, taking him down and making the arrest.
Dong-woo’s former mentor, Commissioner Moon, arrives and insists he return to Seoul. Several people, including Jenny (whose real name is Jae-hee), have gone missing, and Moon wants Dong-woo on the case. Dong-woo is reluctant to return, still nursing distrust in the force after the botched drug raid, but Moon insists he hasn’t wasted his talents. Dong-woo reluctantly agrees, getting the case file.
Back in the city, Dong-woo’s investigation takes him through social media posts of club-goers, showing Jenny running from the bouncers. He’s interrupted by a hospital call, rushing to his daughter, Kang Ye-seo, who’s on suicide watch due to bullying at school. He finds her with a needle mark on her wrist, and a tattoo of a crying woman.
Dong-woo’s estranged wife arrives, blaming him for their daughter’s condition. She accuses him of neglect, blaming him for the bullying and an accidental death on a rooftop.
The next day, Ye-seo reaches out, asking Dong-woo to pick her up after her discharge. She’s distant but needs his help finding Jae-hee. Dong-woo is unconcerned, but Ye-seo is frantic, revealing she can’t live without Jae-hee. She sends a photo, showing the same wrist tattoo.
A flashback reveals a year ago when Ye-seo tried to get Dong-woo to help Jae-hee. The encounter went badly, as Dong-woo judged Jae-hee harshly, accusing her of being a delinquent. Their strained relationship only worsened, with Dong-woo blaming Jae-hee for the rooftop tragedy.
In the present, Dong-woo reconnects with an old colleague, Ji-su, who confirms that Jae-hee has a minor charge of larceny. Ji-su also recognizes her tattoo from a video posted by an illegal spycam group. Meanwhile, Gil-ho has Jae-hee in his care, after finding her passed out in a club bathroom.
Dong-woo and his team encounter Gil-ho from a previous raid. During that bust, one of the club’s customers was abusing an escort, who was later hospitalized. Gil-ho reacts violently, beating the man, but the cops arrest him. However, Dong-woo lets him go, warning him not to cross his path again.
Dong-woo discovers that Ji-su can’t access the plates on Gil-ho’s car because the prosecution has blocked it, and they’re now handling the case. Prosecutor Min Seo-jin arrives in Gangnam and insists on handling the missing persons case alone, to the surprise of everyone, including her boss, Chief Prosecutor Tak.
Meanwhile, Gil-ho tortures Lemon for information and learns that Jung-hwa has been taken to an “event” with the VIPs. As the story unfolds, a man wearing white snake leather shoes enters the hotel room, and Jenny’s life is hanging in the balance. The episode concludes with Gil-ho finding Jung-hwa’s lifeless body in the room, setting the stage for more twists in the next episode.
Gangnam B-Side Episode 2:
The episode opens with a cleaning crew finding Jung-hwa’s body missing from the hotel room, causing panic. Her thug dealer, Psyche, informs Noh Joon-seo, who is more focused on tracking down Jenny. Joon-seo, a beloved but troubled K-pop idol known as Jjuni Boy, is revealed to be behind the chaos.
Gil-ho, on the other hand, dumps Jung-hwa’s body at a subway station, alerting the cops. Dong-woo returns to the Gangnam squad but is sidelined by his colleagues. Despite being kept out, Dong-woo continues his investigation, reaching out to Jang-ho, who’s now a small-time gangster.
Jang-ho reluctantly agrees to help, revealing that Gil-ho has turned into a pimp, with Jenny and Jung-hwa as his top girls. As Dong-woo digs deeper, he uncovers a trap involving Jenny and Joon-seo, while Gil-ho tries to stay one step ahead, determined to avenge Jung-hwa’s death.
At the same time, Prosecutor Min begins tracking CCTV footage of Gil-ho dumping Jung-hwa’s body, leading to a tense confrontation. It’s revealed that Chief Yun, the former Chief arrested by Dong-woo, is now back in charge of Major Crimes, complicating matters for everyone involved.
Gil-ho, unaware of the trap set for him by Psyche, faces off with his enemies in Yeoksam. A brutal fight ensues, streamed for Joon-seo’s enjoyment. The episode reaches its peak when Dong-woo arrives just in time to save Gil-ho, but the situation only escalates.
The episode ends in a dramatic cliffhanger as Gil-ho, cornered by Captain Yun’s squad, jumps into the river to escape, leaving his fate uncertain.