Captain Martin from the police's child department and his colleague Kraus are called to Znojmo to help solve a case regarding stolen toys found in the town's subterranean passages. The members of the local police department are convinced that the thieves are the well-known "customers" from the Znojmo elementary school, pupils Exner and Mandlík. Martin, however, has doubts about these culprits. These doubts grow even stronger after the local self-service shop is robbed and the local tobacco store reports that it is missing a lot of imported cigarettes. Martin questions the children, inspects both shops and searches through the underground.
It is the summer holiday and little Mísa Horák has taken a few animals from the school's so-called "Corner of Living Nature" home to care for. But when he brings home two Angora rabbits, a starling, a little monkey, a tortoise and a small crocodile, his parents order him to take them away. He is helped by Káta, who offers to place the animals in the child's room of her family's apartment. Mísa leaves for her friend where the animals will hopefully be able to stay. Káta goes shopping. In the meantime, Káta's younger sister Minka wakes up and begins to play with the animals, who gradually run off in disarray.
