Luigi, who is engaged to a rich bourgeois, Cinzia, meets his lovely cousin, Sonia, at the cremation of their grandmother. Six months later, Sonia moves in and enters his life, and gradually succeeds in seducing him. Sonia upsets his life. Now, Cinzia is jealous but he can not resist the seductress.

During a spree of violent killings, a young woman writing a thesis in criminology begins to suspect that her new boyfriend, who is a forensic pathologist, might be a serial killer.

Based on Leo Tolstoy's novel, Father Sergius, Night Sun stars Julian Sands as Sergio, a nobleman in 18th-century Italy who is expected to marry a duchess, Nastassja Kinski. Upon learning that she was previously the King's mistress, Sergio turns his back on society and becomes a monk. While at the hermitage he tries to resist all sexual temptations before him and soon becomes known as a miracle worker. Eventually he succumbs to a young seductress and knowing he is undeserving of the adulation, leaves the hermitage to travel around as a homeless beggar.