Something inexplicable is happening in the French capital. On the doors of apartments of peaceful Parisians in different ends of the city, strange inverted fours appear; and at a busy intersection in the city center, some man reads incomprehensible announcements to the public. At first it seems like harmless pranks and harmless madness. But when, in one of the buildings with the fours behind the door not marked with that number, they discover a corpse, the case is assigned to the senior commissioner Adamberg. And soon the investigator realizes that the story has its roots in a distant past.