In front of theater lighting technician Peter Ryabikov, a first-grade girl runs across the road in front of a nearby watering machine. Pyotr catches her and, wanting to punish her, decides to take her home to her parents. However, when he takes her there, it turns out that it is an orphanage, and the girl, whom her friends call Tonya (her real name is Juliet), is an orphan. Pyotr is no longer young, lives in a communal apartment, has a wife, but no children. Feeling somewhat guilty towards Tonya, he wants to adopt her. So, in the large apartment, where only adults had lived before, a little girl appears who completely changes their monotonous life.