Trotsky brings the foundling Petya to the house of his uncle, Dr. Pyotr Ivanovich, who is struck by the inexplicable resemblance of the boy to someone from the past. Petya is told to stay and is given to the irritable artist Andrey Ivanovich as a model, who is painting an image for the hospital church. Meanwhile, an old fisherman on the embankment beckons the boy back to the sea and a free life. Amid the family quarrels and the doctor's drinking bouts, the mystery of the origin of the Wolf Cub emerges.