"Ivy Apartment" is clearly marked on municipal maps, satellite navigation and all official records as having only 12 floors. But for those few people who live here, or who inadvertently break in late at night, at certain times - such as when a heavy rain pours at midnight, when an electrical failure only flashes emergency lights, or when you are alone in a stairwell or elevator - the elevator buttons and stairwell signs will appear out of thin air with the option to go to the "13th floor".
This floor is never a building floor in the physical sense, but a "psychological space" woven bit by bit with the collective fears and forgotten memory fragments of the entire apartment residents. It is like a silent hunter. Once someone notices its existence, they will be quietly devoured by it and trapped tightly, making it impossible to escape.
