St. Petersburg, January 1900-1906. The young architect Boris Bolotov meets Irina Platonova at a prestigious ball. However, Irina is forced to leave St. Petersburg and return to the estate with her father (a famous sculptor) and brother Vladimir. After some time, Irina's father dies. Natalya Platonova (sister of the sculptor Platonov), despite Vladimir's fierce resistance, takes Irina to her place in St. Petersburg. Irina quickly marries the architect Bolotov. A few years later, an unknown person kidnaps Svetlana, the daughter of Irina and Boris Bolotov. At Natalya's request, retired Colonel Vasily Derbenev intervenes in the investigation. He manages to learn many unpleasant facts from the life of the Platonov family.