Besieged Leningrad, the harsh winter of 1941. Petty officer Nikolai Svetlov is discharged from the hospital after a severe concussion in the hope of returning to the front, but on the orders of the commandant he is sent to guard an object of special importance — a zoo. Every day, zookeepers selflessly fight for the lives of animals, trying their best to feed them. Nikolai, who at first does not accept the commandant's decision, gradually begins to realize how important his mission is. Caring for the Beautiful hippopotamus and other zoo animals becomes the meaning of his life.