Filumena has lived with Domenico for twenty five years, but is to be thrown over for a younger woman. So she pretends to be dying and inveigles him into a "deathbed marriage." When he proves the marriage to be null and void, she informs him she has three grown sons which she has supported by stealing from him and that one of them is his (she won't say which). He tries vainly to discover his true son but even when he "remarries" Filumena, she keeps the secret otherwise he would favour "the true son" over the other two. Eventually Domenico agrees with her and as the play ends they're fully reconciled, with every promise of happiness before them.