Kostya and Olya are university teachers. On vacation at a sanatorium, Olya found a more respectable partner for herself – Sergey. He is a wealthy man obsessed with a healthy lifestyle and active sports. Upon arrival, Olya leaves a note for her husband and leaves the house, blocking all contact with Kostya. Sergey has a daughter, Sonya. Kostya finds nothing better than to try to start an affair with her in order to gain access to Sergey and his new lover. Sonya does not find Kostya very attractive. However, the opportunity to irritate her father at a dinner with her potential stepmother seems tempting. After all, her father recently kicked out her boyfriend Maks for “not being serious.”