Two women meet on a train. Each is running from a deadly secret. When one disappears, the other decides to take her place—for better, or for worse.

Jae-Young has just left everything she’s ever known, not that it was much: her thankless job, her infested apartment, and her abusive boyfriend—who happens to be dead on the kitchen floor. Murder was never the way she envisioned leaving, but times were desperate. Now on a train to the bustling city of Seoul, Jae-Young is hoping to escape her transgressions and just become invisible—safe.

On the train, she meets a chatty mother fleeing with her infant son from an unfaithful husband and hoping to find refuge with the in-laws she’s never met. To avoid further conversation, Jae-Young excuses herself for a moment. When she returns, the woman is nowhere to be found. But her crying child remains with a note, pleading with Jae-Young to take him to his father’s family in a remote province far from Seoul. It’s not an ideal pit stop, but for the sake of the child, she can’t ignore the request.

When Jae-Young arrives, the house takes her by surprise. It’s a gated manor oozing with opulence and the finest luxuries—the kind of place she could only dream of setting foot in. What’s more, the family assumes Jae-Young is their daughter-in-law and invites her to stay. She imagines an easy life in their care, free of worry and fear. And Jae-Young realizes: There’s nothing more invisible than becoming someone else.

But both women have ghosts in their pasts. Though unaware of the rot lurking beneath the shiny veneer of her new life, Jae-Young will do whatever it takes to make sure she never goes back.