Anselmo and Lotario are two friends. Anselmo falls in love with Camila and the two are married. Anselmo reveals to his friend that he has a secret desire to test Camila’s fidelity and wants Lotario to be the one to prove her. Lotario sees the folly of such an undertaking but eventually agrees to his friend’s request. At first he only pretends to woo Camila, but when Anselmo catches him making false claims, Lotario agrees to proceed in earnest. When he is alone with his friend’s wife, he discovers what a beautiful woman she is, becoming enamored and making advances that are less feigned than real. Camila is shocked. She vows to protect her virtue at all costs. Her maid Leonela warns against overconfidence. Eventually Lotario’s pleadings have their effect, and Camila succumbs to his persuasions.

When Anselmo returns Lotario reassures him: his wife has overcome all temptations and remains faithful. Meanwhile, Leonela informs her mistress that she too has a “friend,” who as Camila discovers, is allowed into her room at night. When Lotario sees a man leaving the house early in the morning, he believes Camila has taken another lover. Jealous, he reveals to Anselmo that Camila has invited him to her bedroom. Anselmo agrees to hide behind the arras to observe “the action.” But then, when Lotario learns that the man was Leonela’s lover, he confesses his error to Camila, informing her that Anselmo will secretly witness their “sport.” Camila is shocked but devises a plan. Anselmo hides. Camila enters the room displaying a dagger and threatening violence. Leonela tries to dissuade her. When Lotario arrives, she attacks him. He resists but is unable to wrest the weapon from her hand. She strikes herself instead. The blood flows, the knife falls and she sinks to the floor in a pretended faint. Anselmo, rushing from the curtains, stands in dismay over his wife’s “lifeless” body in utter disbelief.

Camila, back to good health and Anselmo content, all is well until one night Anselmo hears footsteps in Leonela’s bedroom. He enters to see a man leap from the window. He threatens to kill Leonela if she does not tell him who the man is. The maid pleads for her life saying she will tell her master more than he has asked. He gives her until morning to reveal her secrets and then informs his wife of what Leonela has said. Camila rises in the night, gathers her precious jewels and flees from the house. In the morning Anselmo discovers that Leonela is not in her room, his wife is nowhere to be found, and even the servants have gone. In the end Anselmo dies of despair, Lotario is killed in battle and Camila lingers in a convent.