Marcello Mastroianni plays a charming playboy in this part film noir, part psychological thriller, where the men are hard and the women are fast. To appearances he seems a successful art dealer, surrounded by many beautiful and grandiose objects and friends. But he is suddenly taken in by the police and interrogated for days without knowing his crime. They play with his mind and send his guilty conscience through a series of flashbacks, memories he isn't proud of. It seems that his lover, the wealthy Adalgisa De Matteis, has been murdered and he is the prime suspect. Marcello puts on his pretty face but can't hide his dirty laundry. Is he the killer, or just a ladykiller? The film keeps us guessing until the very last second.