Spoiler warning: This article reveals the ending of Mousetrap, including the protagonist’s true identity, what happens during the confrontation on the ship, and the meaning behind the final scene.
The final episode of Mousetrap confirms that Yu Min stole Je Moon-jae’s identity in the present, but it also reveals that the protagonist had stolen Yu Min’s life, work, and past years earlier. Moon-jae survives the final confrontation and legally reclaims his name and home. However, he ultimately ends up isolated, unable to write and trapped inside the lie he created.
The truth about Moon-jae, Yu Min, and Min-yeong
The series dismantles the idea that Moon-jae was originally the victim. The writer’s real name is Park Chan-u. Since his youth, he had assumed the identity of Je Moon-jae, taking the place of his older brother, detective Park Sun-yong, within the family dynamic. Later, he tried to erase that past by starting a fire before a school trip.
During college, Moon-jae became jealous of Yu Min and Min-yeong’s secret relationship. He published a piece that mixed facts and lies about the young woman’s private life. The exposure devastated Min-yeong, leading to depression and a suicide attempt.
While Yu Min was taking care of her, Moon-jae stole his rival’s notebooks, published the story as his own, and won the Best New Writer award. In his books, the protagonist was given Yu Min’s qualities, while his rival was portrayed as the jealous one. Moon-jae’s present-day writer’s block stems from the fact that the talent and memories on which he built his career actually belonged to Yu Min.
The confrontation on the ship and Yu Min’s fate
The final showdown between the two takes place on a ship bound for Jeju. Yu Min plans to disappear and expose Moon-jae to the world as the true impostor. During a physical struggle, Moon-jae decides to kill his rival in order to protect the identity he created.
Yu Min falls into the sea and disappears. Since the police are unable to find his body, Moon-jae claims that he acted in self-defense. Detective Sun-yong, Moon-jae’s brother, realizes that his version of events was staged and accuses him of spending his entire life taking other people’s places. However, with no body, physical evidence of murder, or witnesses, the police are unable to arrest him.
Noja and Sun-yong’s fresh starts
While the protagonist sinks deeper into his lies, other characters find ways to move forward. The loan shark Noja survives a violent fight with the criminal Seung-gyu, but loses the use of his right arm. He refuses the money offered by Moon-jae and decides to start over by working in the fields, choosing to face reality rather than continue running from it.
Sun-yong also tries to make amends. During a mediation hearing, the detective admits that he failed as a husband and father and asks for one last chance to rebuild his family instead of continuing to run away from his mistakes.
The final scene: the manuscript and who knocks on the door
When Moon-jae returns to his apartment, he finds the manuscript for Volume 2 of Mousetrap, which Yu Min left behind. The text is a detailed account of the impostor’s crimes, but it also exposes Moon-jae’s plagiarism and the cruel actions he committed in the past. If it is published, his career will be destroyed. Moon-jae tries to rewrite the manuscript to portray Yu Min as insane, but he discovers that he cannot produce anything without relying on his rival’s talent.
In the final scene, someone pounds violently on Moon-jae’s door. The voice reveals that it is Seung-gyu, who has come to collect an outstanding debt. Moon-jae picks up a knife and, as he looks through the peephole, sees Yu Min’s face.
Yu Min’s appearance is not physical. Instead, it is a manifestation of Moon-jae’s paranoia and guilt. The series ends by showing that Moon-jae may have legally reclaimed his life, but he has turned his apartment into a literal and psychological mousetrap. He remains isolated and haunted, unable to escape the identity and lies he created for himself.