Mr. Cheng, his wife May (Shu Qi) and their son Chi Lo are out apartment hunting. The eager real-estate agent shows them one place after another, but there's always something wrong, none of the places seem quite right. Just when they are about to give up the agent offers to show them one last place.
The apartment is located in a vast modern complex with plenty of room, and most importantly the place itself feels bright and welcoming. It seems almost too perfect. The Chengs don't hesitate for a moment, and soon after they move in.
In the middle of moving in something strange happens. May and Chi Lo are in the lobby and while May is trying to organise the family's belongings Chi Lo is playing by himself. Suddenly he finds himself in the elevator alone, and before he can get out, the doors close and the seemingly possessed elevator takes him away. Desperate to locate her son May searches every floor and suddenly she sees something through an air-vent that chills her to the bone: A strange dark shadow crawling through the elevator shaft!
Something is definitely wrong in the place, and Chi Lo feels it too. Even after May finally finds him and brings him back to the apartment he's inconsolable.
But the family's troubles are far from over. A few days later May and Chi Lo are at a birthday party for one on the local children. All the kids are out playing, but suddenly it begins to rain and they all return from the playground. All except Chi Lo. May runs out into the rain to look for him and suddenly she spots him on the roof of the building, about to fall over the edge. A raggedy boney hand has a firm grip on the boy and slowly pulls him over the edge. May runs to aid Chi Lo, but when she arrives, he's gone.
The police is called in and quickly suspect foul play. They suggest May might need medical treatment, but the young woman remains adamant. Someone or something is crawling around inside the building and it has taken her son!