The story takes place in September–October 1945 in Moscow. The war is over. Vladimir Sharapov, a front-line veteran—the narrator of the novel—has been sent for further service to the militia. Although Sharapov is an experienced intelligence officer, his legal knowledge is limited. Therefore, for training and an internship, he is assigned to one of the operational groups of the Moscow Criminal Investigation Department (MUR). This group is led by Gleb Zheglov and is part of the Department for Combating Banditry (OBB). Zheglov’s group must eliminate the gang “Black Cat.” The gang is called that because after each case, they leave behind at the crime scene either a living black kitten or a drawing of a cat. The gang used to rob citizens, but for some time now they have switched to another “line of business”—now the bandits operate on a large scale and rob grocery stores. At the same time, the group is placed under the supervision of an investigator from the prosecutor’s office, who must solve the murder of citizen Larisa Gruzdyeva.