Ethan Carter
Have you watched the South Korean thriller Mousetrap on Netflix? Let’s dive into that surprising ending together.
This gripping series is adapted from the 2017 Kakao Webtoon Field Mouse, created by Ludovico, with direction by Kim Hong-sun, known for Project Wolf Hunting, and writing by Lee Jae-gon, recognized for A Model Family. The show explores the unsettling theme of “identity laundering” through a ten-episode cat-and-mouse narrative. Who exactly is the enigmatic character referred to as The Rat, and what drives his motives?
We will unravel the intricacies of this story — fair warning, spoilers are ahead.
What is the plot of Mousetrap?
Ryu Jun-yeol as Je Moon-jae in ‘Mousetrap.’ Credit: Yoo Eun-mi / Netflix
Reclusive author Je Moon-jae, portrayed by Ryu Jun-yeol from Reply 1988, faces a harrowing reality when a shadowy figure known as “The Rat” steals his identity, looking strikingly similar to him. The character’s name derives from a Korean folklore cautioning against leaving fingernail clippings exposed, as a mouse could consume them and take on that person’s appearance.
Since the tragic death of his parents, Moon-jae has secluded himself in a lavish Seoul apartment, maintaining a solitary existence with only his friend, accountant Son Su-hyeon (Moo Jin-sung), for company. His world is turned upside down when he loses access to his bank account and mobile phone, realizing that someone has hijacked his identity. With the police closing in on him and a loan shark named No-ja (Sul Kyung-gu) becoming an unexpected ally, Moon-jae finds himself in a precarious situation.
At the same time, hardened detective Park Sun-yong (Lee Kyu-hyung) receives a mysterious tip about a body discovered in the Han River, which implicates No-ja. As tensions rise, Park Seung-gyu (Kim Sung-oh), the leader of an identity theft ring, is also on the hunt, intensifying the chase.
Who is the mysterious character known as The Rat?
Ryu Jun-yeol plays both Je Moon-jae and Seo Yu-min. Credit: Yoo Eun-mi / Netflix
As we reach the series finale, the true identity of The Rat is revealed to be Seo Yu-min, a character Moon-jae encountered during his time in a college literary club. thematically, The Rat also symbolizes Moon-jae himself, who serves as an unreliable narrator, having lost memory of his actions due to medication prescribed by his late mother.
Moon-jae initially joined the literary club under false pretenses, claiming to be a university student to fulfill his mother’s wish of becoming a better person. He and Yu-min formed a close bond, both harboring feelings for their friend So Min-yeong (Song Sui). Notably, Yu-min had allowed Moon-jae to read his story, “The Rat That Ate Fingernails,” along with his personal notebooks, which Moon-jae later plagiarized for the club’s anthology. An early scene highlights Moon-jae’s struggle with writer’s block, staring blankly at a computer screen despite having ample notes. In the finale, he comes to the realization, “None of it was ever mine to begin with.”
Is Je Moon-jae truly who he claims to be?
Detective Park Sun-yong (Lee Kyu-hyung) was once known as Je Moon-jae. Credit: Yoo Eun-mi / Netflix
The answer is both yes and no; the truth is layered and complex.
Throughout the series, it is revealed that Sun-yong was adopted by Moon-jae’s parents when he was just five years old. As the detective recalls, the name “Je Moon-jae” stirs familiar memories. It was the name he was given upon adoption, and he remembers being called by Moon-jae’s uncle Han Hui-su during a flashback at an amusement park. Essentially, Sun-yong has been unknowingly searching for his own brother throughout the series — a fact that Yu-min was aware of, which is why he tipped off the detective.
When Sun-yong (originally Moon-jae) was sent back to the orphanage due to his adoptive parents having a biological child, they chose to name their new son Moon-jae. In the finale, Moon-jae reflects on an incident where he started a fire at school while registered under a different name, Park Chan-u, stating, “It doesn’t feel like my name,” unaware that it had originally belonged to his brother.
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What fate befell Min-yeong?
Ryu Jun-yeol as Moon-jae. Credit: Yoo Eun-mi / Netflix
In one of the most heartbreaking narratives of Mousetrap, Min-yeong’s tragic death is directly linked to Moon-jae’s reckless actions.
During their university years, Moon-jae, Yu-min, and Min-yeong took a summer trip to Jeju Island, known for its breathtaking scenery. During this getaway, Moon-jae’s jealousy flared when he saw Yu-min and Min-yeong bonding. In a moment of drunken impulsiveness, he requested to speak with Min-yeong alone to confess his feelings. When she declined, revealing her secret relationship with Yu-min, Moon-jae’s rage led him to attack Yu-min.
Later, consumed by envy, Moon-jae fabricated a post online detailing fictitious sexual encounters between Min-yeong and Yu-min, which led to Min-yeong being publicly shamed during her graduate studies. Ostracized by her peers, she withdrew from school and severed ties with her family, while Yu-min desperately sought to prove Moon-jae’s involvement to the authorities.
“You must have been one hell of a writer. Even the cops had nothing on you,” Yu-min remarks in the finale.
“I was high on drugs. Who’d read that nonsense? I just wrote it like a story,” Moon-jae responds.
In a bid to support Min-yeong emotionally and financially, Yu-min submitted his unpublished manuscript “The Rat That Ate Fingernails” to a publisher, hoping for its success. he discovered that Moon-jae had already released the work as Interview by Sung Hag-Yun, winning the prestigious Best New Writer award and launching Moon-jae’s career. Tragically, Min-yeong took her own life, and in his grief, Yu-min read Interview by her side, realizing that the narrative mirrored their lives, altered to fit Moon-jae’s perspective.
“You were so envious of me that, in your novel, you subtly switched our identities,” Yu-min states. “So I devised a plan. I will take everything you stole from me. I will become you and expose the truth.”
What is Yu-min’s master plan?
Ryu Jun-yeol as Yu-Min. Credit: Yoo Eun-mi / Netflix
Following Min-yeong’s death, Yu-min embarks on a quest for vengeance. He undergoes plastic surgery to assume Moon-jae’s appearance and meticulously studies his voice.
In a bid to steal Moon-jae’s identity, Yu-min infiltrates Seung-gyu’s identity theft syndicate, selling his own identity in the process. he orchestrates his own death to prevent his identity from being compromised. Yu-min also sells Min-yeong’s identity to Seung-gyu, commits murder, replicates Min-yeong’s tattoo on the victim’s body, and subsequently tips off the police to frame Moon-jae for the crime, aiming to implicate Seung-gyu.
Yu-min coerces Sun-yong into assisting him in stealing Moon-jae’s life (by cloning his phone and cutting off his access to funds), all while holding Sun-yong’s daughter hostage. Tragically, Su-hyeon dies by suicide before Moon-jae can uncover the truth. By the finale, we learn that it was Yu-min who informed Detective Park about No-ja, intentionally placing Sun-yong, who was once adopted by Moon-jae’s parents, in charge of the case that would frame Moon-jae.
When Detective Park investigates university records, he finds no evidence of Min-yeong (because Yu-min sold her identity to frame Moon-jae) or Moon-jae (since he was never a student), but there is a record for Yu-min.
Are both Moon-jae and Yu-min alive by the end of Mousetrap?
The climactic events unfold aboard the Queen Caligo. Credit: Yoo Eun-mi / Netflix
In the series finale, Moon-jae tracks down Yu-min on the Queen Caligo, the ship that serves as the backdrop for their tragic past.
During their climactic confrontation in the ship’s cabin — the same space where the trio shared memories that summer — Moon-jae uncovers the truth, ultimately battling Yu-min and hurling him out the window into the ocean. In this pivotal moment, Moon-jae discovers his true motivation: “I don’t think I wanted to be you. I think I wanted to be myself. A better version of myself.”
The real puppet master is Han Ji-hye, the editor-in-chief at the publishing house, who has been the only person to reach out to Moon-jae in three years. She quickly discerns the differences between the two men simply by being observant. After Yu-min confesses, she hands Moon-jae the unpublished manuscript of The Rat Vol. 2, where Yu-min reveals Moon-jae’s actions, telling the world the story we’ve just witnessed in Mousetrap. “This should never get out,” a panicked Moon-jae reflects in voiceover.
In the closing scene, as Seung-gyu knocks on Moon-jae’s door, we see Yu-min in the square. It’s ambiguous whether Yu-min is truly alive or if Moon-jae is haunted by his guilt, envisioning him. it’s evident that Moon-jae’s efforts to escape his past have been in vain.
Mousetrap is available for streaming on Netflix.
Daniel Mercer
Brandon Fletcher
