Netflix’s ‘Mousetrap’ ending, explained | Mashable

Watched South Korean thriller Mousetrap on Netflix? We need to talk about that ending.

Based on the 2017 Kakao Webtoon Field Mouse by Ludovico, directed by Kim Hong-sun (Project Wolf Hunting), and written by Lee Jae-gon (A Model Family), the series takes the chilling concept of “identity laundering” and turns it into a 10-episode cat-and-mouse game. But who is the series’ core mystery figure known as The Rat and what’s his motive?

Let’s break it all down — and suffice to say, spoilers ahead.

What is Mousetrap about?

Reclusive novelist Je Moon-jae (Reply 1988‘s Ryu Jun-yeol) finds his identity completely stolen by a mysterious figure known as “The Rat,” who looks exactly like him. He takes his moniker from the Korean folktale that warns children against leaving their fingernail clippings lying around — if a mouse eats them it can transform into that person’s likeness.

Moon-jae has been a total recluse since his parents’ tragic death, and thanks to his literary success, his hideaway is a luxurious apartment in Seoul, where his only real connection to the outside world is his friend, accountant Son Su-hyeon (Moo Jin-sung). Suddenly, Moon-jae can’t access his bank account or his phone, quickly realising his identity has been hijacked, the cops are on his trail, and a loan shark called No-ja (Sul Kyung-gu) is his only ally.

Meanwhile, hardened detective Park Sun-yong (Lee Kyu-hyung) receives an anonymous tip about a body found in the Han River, one that points the finger at No-ja, who is, in turn, pursued by identity fraud ring boss Park Seung-gyu (Kim Sung-oh). Thus, the chase is on.

Who is The Rat?

Ryu Jun-yeol plays both Je Moon-jae and Seo Yu-min.
Credit: Yoo Eun-mi / Netflix

By the finale, we learn that the Rat is a man called Seo Yu-min, whom Moon-jae met an intercollegiate literary club. But the real Rat, thematically, ends up being Moon-jae himself, an unreliable narrator who has forgotten his actions due to taking his late mother’s medication.

Moon-jae joined the literary club by faking being a university student, to “become a better version of myself, like my mom always told me.” Moon-jae and Yu-min became close, both crushing over their friend So Min-yeong (Song Sui). Notably, Yu-Min let Moon-jae read his story, “The Rat That Ate Fingernails,” and read his notebooks, which Moon-jae later stole and submitted for the club’s anthology as his own work. To hammer it home, there’s a scene early in the series where Moon-jae is seen sitting at his computer unable to type anything. Though he’s surrounded by notes, he stares at a blank page, a blinking cursor. “None of it was ever mine to begin with,” he realises in the finale.

Is Moon-jae actually Moon-jae?

Detective Park Sun-yong (Lee Kyu-hyung) was once called Je Moon-jae.
Credit: Yoo Eun-mi / Netflix

Yes and no. It’s complicated.

Throughout the series, we learn that Sun-yong was actually adopted by Moon-jae’s parents when he was five years old, as the detective remembers why the name “Je Moon-jae” felt so familiar to him. It’s the name he was given when he was adopted, and one he remembers being called by Moon-jae’s uncle Han Hui-su in a flashback to a theme park. Essentially, Sun-yong has been unknowingly hunting his own brother for the whole series — a fact Yu-Min definitely knew, hence why he tipped off the detective personally.

Sun-yong (then Moon-jae) was sent back to the orphanage when his adopted parents bore a son, and because they apparently really liked the name (or wanted to conceal their actions), called their biological child Moon-jae. When Moon-jae visits No-ja in the finale, he recalls a time he started a fire at a school, where he’d registered under a different name, Park Chan-u. Why? “It doesn’t feel like my name,” he felt at the time, despite not knowing it was first his brother’s.

What happened to Min-yeong?

Ryu Jun-yeol as Moon-jae.
Credit: Yoo Eun-mi / Netflix

In probably the saddest tale of Mousetrap, Min-yeong’s death is framed as directly caused by Moon-jae’s actions.

Back in their university days, Moon-jae, Yu-min, and Min-yeong went on a summer trip to Jeju, a picturesque island off the south coast of the Korean Peninsula. During the trip, Moon-jae became jealous of the other two spending time together, and in a drunken state, asked to speak to Min-yeong alone to declare his feelings. Refusing, she revealed that she and Yu-min had always been a secret couple, before Moon-jae met them. Moon-jae lost control and attacked Yu-min.

Later, in an envious rage, Moon-jae wrote a post in an online forum fabricating sexual details of Min-yeong and Yu-min’s relationship, after which she was shamed at grad school by her peers. Socially ostracised, she dropped out and cut ties with her family, with Yu-min desperately trying to prove to the police that Moon-jae wrote it.

“You must have been one hell of a writer. Even the cops had nothing on you,” Yu-Min says in the finale.

“I was high on drugs. Who’d read that bullshit? I just wrote it like a novel,” Moon-jae says.

Emotionally and financially supporting Min-yeong, Yu-Min sends his unpublished novel “The Rat That Ate Fingernails,” to a publisher hoping for a runaway success — only to find that his work had already been published as Interview by Sung Hag-Yun, which won Moon-jae a prestigious Best New Writer award and launched his career. Sadly, Min-yeong dies by suicide, and in a state of despair, Yu-min reads Interview by her side, only to find the story resembles that of their lives, with Moon-jae changing the details to his own perspective.

“You were so jealous of me that, in your novel, you subtly made yourself me and me you,” Yu-Min says. “So I decided. I’ll get my revenge. I’ll become you too and take back everything you took from me. I’ll rip that mask off your face, strip you of everything, and throw you out.”

What’s the Rat’s plan?

Ryu Jun-yeol as Yu-Min.
Credit: Yoo Eun-mi / Netflix

After Min-yeong’s death, Yu-min goes to vengeful extremes. He gets plastic surgery to look like Moon-jae and learns how to speak using his voice.

To steal Moon-jae’s identity, Yu-Min found his way into Seung-gyu’s identity fraud ring, selling his own identity. However, Yu-Min faked his own death before his identity could be laundered. He also sold Min-yeong’s identity to Seung-gyu, murdered a random woman, replicated Min-yeong’s tattoo on her body, then tipped off the cops to frame Moon-jae for murder and implicate Seung-gyu.

Yu-Min then forced Sun-yong to help him steal Moon-jae’s life (cloning his phone, blocking access to his money etc.), as the Rat kidnapped his daughter. Su-hyeon dies by suicide before Moon-jae can get more answers. By the finale, we know Yu-Min is the one who sent the tip about No-ja to Detective Park, as he wanted Sun-yong to be the lead detective on the case that would frame Moon-jae for murder (Detective Park was once adopted by Moon-jae’s parents.)

When Detective Park checks the university records, there’s no record of Min-yeong (because Yu-Min sold her identity to frame Moon-jae) or Moon-jae (because he wasn’t a student), but there is one for Yu-Min.

Are both Moon-jae and Yu-Min alive at the end of Mousetrap?

Everything goes down in the Queen Caligo.
Credit: Yoo Eun-mi / Netflix

In the finale, Moon-jae tracks Yu-Min down to the Queen Caligo, the ship bound for Jeju, where it all began.

In their final confrontation in the ship’s cabin (the same cabin the trio stayed in that fateful summer), Moon-jae learns the truth, ultimately fighting with Yu-Min and throwing him from the window into the sea. In this scene, Moon-jae finally finds his motivation: “I don’t think I wanted to be you. I think I wanted to be myself. A better version of myself.”

The one really holding the cards here is publishing house editor-in-chief Han Ji-hye (The Call‘s Lee El), the only person who talked to Moon-jae in the last three years, and who quickly works out the difference between the two by simply being observant. After Yu-Min tells her the truth, she gives Moon-jae the unpublished manuscript of The Rat Vol. 2, in which Yu-Min exposes what Moon-jae did, telling the world the story we just watched in Mousetrap. “This should never get out,” a panicked Moon-jae says in voice over.

In the final scene, however, when Seung-gyu finds Moon-jae’s apartment and bangs on the door, we see Yu-Min in the square. It’s not clear whether Yu-Min is actually alive or whether Moon-jae’s guilt is making him experience a vision of him. But it’s clear Moon-jae’s attempt to outrun his past has failed.

Mousetrap is now streaming on Netflix.