Homicide detective Kamenár can't find his place in the world following the death of her daughter. His marriage has fallen into pieces; while his wife has found consolation in religion, he buries himself in his work and lives a self destructive life. One day he's called on the scene of a brutal murder. It turns out quickly that he knows the prime suspect quite well: Petra was his daughter's best friend and supposedly the responsible person for her death. With revenge appearing in his sight, Kamenár's life gains new purpose and he's willing to move mountains to prove the girl guilty in this new case, no matter how determined she is about her innocence. As the investigation progresses, Kamenár has to face more and more disturbing revelations. He must make his mind up whether Petra is actually innocent or so professional that she's able to commit the perfect murder.