Former primary school teacher Ksenia Malykhina disappeared. Her son applied to the police. Operational officers Captain Timur Ovchinnikov and his partner Vasily Kireev decided to inspect the apartment of the missing, in which she lived alone, and at the same time interview the neighbors. The teacher's neighbor, having examined the apartment, did not notice anything unusual. She was about to leave when she accidentally looked into the bathroom and cried out. The bath was completely black, without the slightest sign of enamel. The operatives ambushed the apartment. At night, they heard someone open the front door...