A Tri-City beach becomes a place of dramatic discovery when the sea washes up the body of a young girl. The victim's unusual mutilation points to murder. The investigation is headed by an ambitious and tenacious prosecutor, Leopold Bilski. The victim's mother, Judge Helena Bogucka, is also involved in the investigation. All clues lead to one of the seaside clubs, which turns out to be related to the murder of a woman from 15 years ago. From the information collected during the investigation and the evidence concealed for years, the dark face of the criminal Tri-City slowly emerges. Bilski and Bogucka's discoveries begin to be very inconvenient for the local police..