Chen Xiansheng has been taught since he was a child: the fourth door at home should never be opened. Twenty years ago, it devoured the twin sister he had never met. The father went crazy and the family was broken up.
Now, his father died mysteriously, and Chen Xiansheng was forced to return to the old nightmare house of his childhood. While sorting out the relics, he accidentally opened the forbidden door - what was behind the door was not a wall or a room, but a dark and twisted alien space that was a complete mirror image of his home.
Here, whispers echo off the walls and shadows take on a life of their own. What frightened him the most was that the "sister" who was supposed to be dead was standing at the end of the corridor, smiling at him...
