Having casually overheard a confusing phone conversation between two women, Alberto manages to get in touch with one of the callers, Claudia, a painter. The two become lovers and things are spiced up by Claudia's ambiguous sexual nature and by the presence of her former lover, Pietro. Alberto discovers a pistol in Claudia's handbag and this leads to a further revelation: she's dominated by her stepmother Greta, who forced her into a clandestine lesbian relationship; of which Claudia is ashamed and wants to end - at all costs. Alberto, now a slave to love, runs Greta over. But Claudia denies urging him to murder...