Something inexplicable is happening in the French capital. Strange inverted fours appear on the doors of the apartments of peaceful Parisians in different parts of the city, and at a busy intersection in the city center a man reads incomprehensible announcements to the public. At first it seems that these are harmless pranks and harmless madness. But when a corpse is discovered in one of the four houses, the case is entrusted to Senior Commissioner Adamsberg. And the detective soon becomes clear that this whole story has roots in the distant past.