A week after the tragic death of Anatoly Ivanovich, his son Sergei is experiencing a new shock. He receives a letter from his mother, whom everyone considered long dead. Mother tells Sergey that his father left her, hopelessly ill with tuberculosis, almost thirty years ago. However, she survived, for many years she experienced many adversities and now she decided to find a son. Sergey is happy. He brings his mother to his house. But for some reason, she did not immediately have a relationship with her daughter-in-law. Sergey’s wife does not trust Valentina, it seems to her that there is something strange behind the appearance of this woman. Olga is trying to find out what happened in the Korostylev family thirty years ago. She goes to the city where Sergei spent his childhood. The truth, which she gradually opens up, turns out to be a real barrel of dynamite. Olga understands that she urgently needs to save her family. But will she be able to get out of this city alive?