Wuyin Town is about to be completely submerged by a reservoir project. After his grandmother dies, Chen Du returns to the small town where he has lived for eighteen years to keep vigil over her body. On the night of the funeral, he receives a black handbook his grandmother left behind.
The first page reads:
If you hear someone knocking on the coffin tonight, do not open the door.
If the knocking comes from inside the coffin, find someone to take over the vigil before dawn.
Remember: the dead never knock four times in a row.
At midnight, the fourth knock comes from inside the coffin.
