Young cinematographer Stefano and his wife Alina, who cannot have children, sincerely love each other, but have made the pact of being an "open couple"; that is to be able to betray oneself freely. Even if he has some quick and occasional adventures, it is above all the woman, restless and dissatisfied, who seeks other emotions, and therefore, having become the lover of the musician Paolo. She tells her husband that she has decided to divide the week between two men. Despite suffering deeply, Stefano, who loves her very much, accepts her decision, but from that moment on he is tormented by all the pains of jealousy.