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.

An animal lover, Miloš , brings a small mouse to school, which causes a lot of excitement in the classroom. Miloš remains for punishment after school, however, when the teacher notices that Miloš is bringing lunch to his sick grandmother, she lets him go home. However, Miloš cannot get home with lunch. Somewhere, he lost the key he wears on the string around his neck.