Mousetrap: The Korean Folktale Behind Netflix's New Drama

Clip your fingernails, toss them out carelessly, and a field mouse eats them — the mouse becomes you, walks into your house, and your own family takes its side. That old Korean folktale is the engine under Mousetrap, the mystery thriller Netflix releases worldwide on August 28, 2026. Nearly every English preview of the show stops at the logline and the cast list. The tale underneath has a formal name, a place in Korean folklore scholarship, and an ending that hinges on a cat — and it tells you more about where this story is headed than any teaser does.

Quick answers

• Mousetrap premieres worldwide on Netflix on August 28, 2026, directed by Kim Hong-sun and written by Lee Jae-gon.
• It is built on the Korean folktale of the fingernail-eating field mouse: a rat that eats a person’s discarded nail clippings turns into that person and takes over their life.
• Ryu Jun-yeol stars as Moon-jae, a reclusive novelist whose name, face and entire life are stolen, opposite Sul Kyung-gu as a loan shark and Lee Kyoo-hyung as a detective.

What Is Mousetrap, the New Netflix Korean Drama About?

Mousetrap is a mystery chase thriller about a shut-in novelist who loses his identity piece by piece to a stranger wearing his name and his face. Netflix’s own description sets it up plainly: Moon-jae has not left home in years, and then the small things start going wrong — his fingerprint will not unlock his phone, his passwords stop working, and one by one the things tying him to his own identity slip out of his grasp. Closing in from the other direction are Noja, a loan shark trying to recover money that vanished along with the old Moon-jae, and Sun-yong, the detective working the case. The tagline compresses the whole predicament into one line: “Prove I’m real, or I’m the imposter.”

What Is “The Rat That Ate Fingernails,” Exactly?

It is a transformation tale in which a rat that has spent years eating a householder’s discarded fingernails and toenails becomes a perfect double of him and takes his place. Korean folklorists file it as 쥐둔갑 설화 (jwi-dungap seolhwa, “rat shapeshifting tale”), also known as 진가쟁주 (jinga-jaengju) — the true master and the false master fighting over whose house it is. The Encyclopedia of Korean Culture describes the shape the story takes almost everywhere it was collected: the family believes the impostor, the local magistrate hears the dispute and rules against the real man, and the genuine householder is driven out of his own home. He wanders, ruined. Only after a helper tells him what to do does he return — carrying a cat. The cat kills the double, the body reverts to a rat, and the man gets his life back.

What gives the tale its bite is the middle act, not the ending. The horror is not the monster; it is the hearing, where being right counts for nothing because everyone who loves you has already picked the other man. Versions were collected from across the country and published in the Korean Oral Literature Survey between 1980 and 1988.

Why Did Koreans Treat Clipped Fingernails as Part of a Person?

Because hair and nails were understood as something received from your parents rather than waste your body threw off, so scattering them was a small act of disrespect and not merely untidiness. The Encyclopedia of Korean Culture draws the line directly: the taboo around treating hair and nails carefully is formed by ideas about filial piety. That places it in the same moral frame as the deference rituals that still shape Korean daily life, where the body itself is inherited property held in trust. Read that way, the folktale is not really about a rat at all. It is a warning about being careless with the pieces of yourself, because someone else can pick them up and put them on.

Newcomers will find this the single most useful thing to know going in, since it explains why the premise reads as dread rather than as a gimmick for Korean audiences. Nail clippings are not a random magical ingredient like a wizard’s newt eye. They are the closest thing the folk tradition has to a stolen ID.

Which Parts of the Premise Come Straight From the Tale?

Three of them: the stolen name, the impossibility of proving yourself to the people who should know you best, and an authority figure who sides with the copy. Director Kim Hong-sun has said the work is “motivated by the folktale of the fingernail-eating rat” and called it “a thriller about a man whose life has been stolen trying to reclaim his identity.” Ryu Jun-yeol, who plays a dual role according to Korea Times, has said he remembered reading the original folktale as a child.

The updates are where it gets clever. In the old story the impostor is undone by a cat; here the machinery of proof is biometric and bureaucratic — a fingerprint that will not read, a password that no longer works. A magistrate’s verdict becomes a detective’s case file. Kim has pointed to one line as the thesis of the whole drama: “life is like an island.”

Who Stars in Mousetrap, and Who Made It?

Three actors carry it, with Ryu Jun-yeol at the centre and two very different pursuers closing in. Netflix’s newsroom credits Kim Hong-sun as director and Lee Jae-gon as writer.

Name	Role
Ryu Jun-yeol	Moon-jae — the reclusive novelist whose identity is taken
Sul Kyung-gu	Noja — a loan shark chasing money that disappeared with Moon-jae
Lee Kyoo-hyung	Sun-yong — the detective pursuing the case
Kim Hong-sun	Director
Lee Jae-gon	Writer

As of 2026, Netflix bills the series as a mystery chase thriller, and the word “chase” is doing real work there: Korea Times reported that the adaptation restructures the webtoon into a pursuit format rather than a slow-burn mystery.

Is Mousetrap Based on the Field Mouse Webtoon?

Yes — Netflix credits the webtoon Field Mouse as its source, and on Kakao Webtoon the series is credited to the artist 루드비코 (Ludvico) and shelved under horror and thriller. The Korean title of both the webtoon and the show is 들쥐, which literally means “field mouse,” the exact creature named in the folktale: 손톱 먹은 들쥐, “the field mouse that ate fingernails.” The English title moves the emphasis from the animal to the trap, which is a fair summary of what the premise does to Moon-jae.

Webtoon-to-screen adaptations are common enough now that the source is often the best spoiler-free preview available, the way readers of Villains Are Destined to Die knew that ending long before anyone else. Going in cold is also a perfectly good plan.

Frequently Asked Questions

Q: When does Mousetrap come out on Netflix?

Friday, August 28, 2026, worldwide on Netflix. That date comes from Netflix’s own newsroom announcement rather than from fan aggregators.

Q: What Korean folktale is Mousetrap based on?

손톱 먹은 들쥐, “the field mouse that ate fingernails.” A rat eats a man’s discarded nail clippings, becomes his exact double, takes over his household, and is only exposed when the real man returns with a cat.

Q: Do I need to know the folktale to follow the show?

No. Knowing it tells you what the story is actually about — proving you are yourself to people who no longer believe you — and Korean viewers will be carrying that context from the opening scene.

Q: Is Mousetrap a horror series?

Netflix classifies it as a mystery chase thriller rather than horror, though the source webtoon sits on Kakao Webtoon’s horror and thriller shelf.

Q: Who does Ryu Jun-yeol play in Mousetrap?

Moon-jae, a novelist who has not left his home in years and whose name, face and life are taken from him. Korea Times reports that Ryu plays a dual role.

Ahead of the premiere, the smartest prep is not a recap video — it is knowing that when Moon-jae cannot prove he is himself, he is re-enacting an argument Korean storytellers have been staging for generations. Queue up The Apartment Job if you want another Netflix Korean drama explainer to fill the wait.