The Intruder is a story of the dandy Tullio Hermil, unfaithful to his patient and loving wife, Giuliana. Tullio is a Nietzschean superman. He is handsome, intelligent, and powerful. Also, he believes himself to be superior to other men and beyond the reach of their judgment. Therefore, he ignores the feelings of others, not to mention his own wife. Yet, at some point, growing weary of his debauchery, Tullio decides to attempt a reconciliation with his wife. Giuliana is patient and loving and forgives his husband's sins. In a single weak moment, Juliana has succumbed to another man's advances and has gotten pregnant. As Tullio learns about that, he gets furious. When the baby (the Intruder) is born, Tullio starts thinking of a horrible crime. Yet, he must find the courage to commit it.