The Devil's Daughter (1952)

Garibaldi, after landing in Marsala, moves on to Naples. The liberals are overjoyed but the Bourbons are terrified. The so-called Baron Tucci, on a recommendation from England, arrives at the home of Count Sereni, a notable liberal. But he turns out not to be a patriot who has returned to Italy to take part in the fight but a degraded Bourbon official who has been promised rehabilitation if he can succeed as a spy. Tucci discovers old Sereni's second wife is one of his former lovers and persuades her to murder her husband so as to gain his inheritance. She does indeed cause the count to die, by withholding his heart medicine, but not before he destroys his will.