Misplaced Apartment at Midnight

The protagonist moves into an old apartment and discovers that every time at 12 o'clock in the evening, if someone presses the "1" floor and "top floor" buttons of the elevator at the same time, the elevator will reach a non-existent "misplaced floor". The layout of this floor is exactly the same as that of the protagonist, but the details are different, and it is possible to encounter "other" residents inside - they seem to be past or future residents of the apartment, or even... People who are supposed to be dead.