Having recently moved into a new apartment with her loving but distracted and preoccupied parents, Coraline finds herself bored one rainy day and, upon her father's suggestion, decides to explore the flat. She finds a locked door in the drawing room, which her mother opens and explains once led to the flat next door but was bricked up when the building (which was once a single house) was separated into apartments. That night, Coraline hears a strange noise and sees a small black shadow slip down the hall outside her bedroom and into the drawing room. When Coraline turns on the light, it has vanished, but the door, which was previously closed by her mother, is slightly cracked.
The next day she takes her mother's key and opens the door to find, instead of a brick wall, a dark corridor which leads to another apartment, seemingly a twisted copy of her own. This alternate world is inhabited by her Other Mother and Other Father, who are almost exact physical duplicates of her real parents. The only difference: a pair of black buttons sewn in place of their eyes.