The central twist of "Toto, Peppino, and the Hussy" is that the titular "hussy," Marisa Florian, is not a villainous seductress but a kind and sincere woman who genuinely loves Gianni. The entire premise is built on the false assumption propagated by an anonymous letter from a jealous girl. When Antonio and Peppino finally confront Marisa, their elaborate, intimidating plan, built up through the famous letter-writing scene, crumbles in the face of her genuine emotion and grace.
After receiving their garbled but still hurtful letter and a sum of money, Marisa is heartbroken. Gianni finds her and, to prove his love and the depth of his feelings, he sings "Malafemmena" to her in front of a theater audience. The song, written by Totò himself, is about a man's heartbreak over a "bad woman" he can't help but love. In the context of the film, Gianni's heartfelt performance reclaims the term, showing Marisa that his love is true despite his family's opinion. The raw emotion of the performance deeply moves Marisa. Crucially, Gianni's mother, Lucia, witnesses this moment and realizes the couple's love is authentic and that Marisa is a good person.
In the end, Lucia overrules her brothers' objections. The family accepts Marisa, who happily agrees to give up her career in the revue. The final scene shows Marisa fully integrated into the Caponi family, having moved to their rural village to marry Gianni. The supposed "hussy" becomes the perfect daughter-in-law, completely subverting the brothers' initial, ignorant fears and prejudices.