The South Korean drama Mary Kills People (메리 킬즈 피플) airs episodes 3 and 4 on August 8 and 9, 2025. The show features Lee Bo-young, Lee Min-ki, and Kang Ki-young. Written by Lee Soo-ya and directed by Park Joon-woo, Mary Kills People is a remake of the 2017 Canadian original.Mary Kills People explores the complex life of a respected physician who covertly helps terminal patients end their suffering. Meanwhile, a dedicated detective begins probing the increasing number of unexplained deaths linked to her.Disclaimer: This article contains spoilers. Reader discretion is advised.In previous episodes, Woo So-jeong decides to help Cho Hyeon-u, who is suffering from terminal cancer, pass away. However, in episodes 3 and 4 of Mary Kills People, she learns that the Cho Hyeon-u she knows is an undercover detective, and he is using the identity of another man.Mary Kills People episodes 3 & 4 recaps: Undercover mission, and a hospital escapeStill from the show (Image via X/@mbcdrama_pre)Episode 3 of Mary Kills People opens with a flashback to three months before the incidents in the previous episodes of Mary Kills People. Cho Hyeon-u (Lee Min-ki), also known as former detective Pan Ji-hun, has been demoted to traffic police duty.One day, his former teammates from the force approach him with a mission to go undercover and gather evidence against Woo So-jeong. Initially reluctant, Hyeon-u accepts when he learns that powerful figures are backing the operation. He assumes the identity of a dying man, Cho Hyeon-u, and, as planned, approaches So-jeong.The timeline of this episode of Mary Kills People then shifts back to the present, where Hyeon-u is speaking with So-jeong in a church. She promises to help him. However, due to the earlier confrontation with a patient’s husband, the euthanasia drug ampules in So-jeong’s possession break, leaving only one intact.The next day, the police begin creating a fake home for Hyeon-u. The idea is to stage it as his favorite place so they can lure So-jeong into performing euthanasia for him there, catching her in the act.Meanwhile, Ryu I-su, Woo-mi’s mother and a lawyer, discovers that her daughter has taken a drug before a performance. Further, she learns that she stole the drug from So-jeong’s home.Still from the show (Image via X/@mbcdrama_pre)She also finds out that So-jeong had deleted all of Woo-mi’s medical files from the hospital. Furious, I-su confronts So-jeong, but So-jeong refuses to apologize, insisting that Woo-mi has stolen the ampule herself. I-su, however, vows to make her pay.The footballer’s wife visits the hospital to thank the doctors who have treated her husband. She hands over all files related to So-jeong’s euthanasia work with her husband and expresses her gratitude for So-jeong’s help.Elsewhere, Choi Dae-hyeon is helping a terminally ill high school client, Cho Su-yeong (Lee Won-jung), fulfill his last wish, which is to confess to his crush. They meet the girl, who already knows of his feelings and is aware of his condition.She breaks down in tears. During the conversation, Su-yeong’s health suddenly worsens, and Dae-hyeon rushes him home. On the way, the boy says he’s so happy that he wants to die that very night.At the sting house set up by the police, So-jeong arrives, unaware of the hidden cameras and the police van stationed nearby. As Hyeon-u settles in, So-jeong receives a call from her church’s father informing her that “Cho Hyeon-u” has died.Realizing that the real Cho Hyeon-u, whose identity Hyeon-u (aka Pan Ji-hun) is using, has been identified, she grows suspicious. She excuses herself, saying she needs to get something from her car. Outside, she notices the police van and immediately escapes, destroying the last remaining ampule.Shortly after, Dae-hyeon tells her about Cho Su-yeong’s wish to die that night. So-jeong explains she’s out of ampules and goes to Dae-hyeon's drug supplier. She makes a deal with the dealer, Go Kwang-cheol, and secures new ampules. That night, Su-yeong says goodbye to his father. So-jeong and Dae-hyeon help him pass away.On this note, episode 3 of Mary Kills People ends.Still from the show (Image via X/@mbcdrama_pre)Episode 4 of Mary Kills People begins with So-jeong and Dae-hyeon discussing Xiuying’s death. So-jeong recalls the deal with Go Kwang-cheol in exchange for the ampules. He forced her to strip off her top at gunpoint and has taken a compromising photo as leverage.Meanwhile, news breaks that a major drug dealer, Gim Si-hyeon, has been caught. However, Hyeon-u is unconvinced that the arrested man is the real Gim. The legislator behind the mission against So-jeong is also furious at their failure to catch her and orders a hospital raid under a different case.During the raid, Hyeon-u confronts So-jeong, warning her to stop or he will have to arrest her for murder. She snaps back, telling him he will never understand her work and will never catch her. Her words trigger memories of his senior officer, who has taken his own life in front of the team after being accused of a crime.So-jeong decides to pause her euthanasia work for now. She suggests that Dae-hyeon and Nurse Choi Ye-na volunteer at the church so they can meet discreetly and use that as a cover if questioned.Still from the show (Image via X/@mbcdrama_pre)Later in this episode of Mary Kills People, So-jeong and Ryu I-su cross paths at a meeting for parents of the class attended by I-su’s daughter and So-jeong’s niece. An Tae-seong is also there and alarmed by So-jeong’s presence, tries to dig for information about Woo-mi’s collapse. He indicates his suspicion of drug usage. However, So-jeong dismisses it, saying it is caused by extreme dieting.Elsewhere, the real Gim Si-hyeon, who works with Go Kwang-cheol, begins causing problems for Go. Go decides to eliminate him and orders a hitman. The attempt fails, however, and Gim escapes with a bullet wound.He is taken to So-jeong’s hospital. While she treats him, the police are called in to question him. With them, Hyeon-u arrives and immediately recognizes him as the real Gim Si-hyeon and calls for backup.Go Kwang-cheol knows Ahn Tae-seong and blackmails him not to take action against Gim Si-hyeon. Go then calls So-jeong, blackmailing her into helping Gim escape before Hyeon-u and his team arrive.Reluctantly, she complies and hands Gim a pair of scissors to hold to her neck. Staging a hostage situation, she leads him out to Go’s waiting car. Just as they get in, Hyeon-u and his team arrive, but the car speeds off with Gim and So-jeong inside, leaving them unable to intervene.With this, episode 4 of Mary Kills People concludes.Mary Kills People is broadcast every Friday and Saturday at 10 pm KST on MBC TV. Episodes 5 and 6 are set to air on August 15 and 16, 2025.