Children's speech therapist Dina has a happy and measured life: her daughter Olya and her beloved man Sergey, with whom she has long been planning to legalize her relationship. Dina met her best friends - Nelya, Yana and Anna - in her first year of pedagogical school, and since then they have been inseparable. Everything changes when Yana dies under strange circumstances, and her husband accuses Dina of the crime. And now the heroine, together with Nelya and their new acquaintance, investigator Evgeniy, must understand this complicated case in order to prove her innocence. But Dina will have to look for her friend's killer in secret from her beloved man.