What Ever Happened to Baby Toto?

A pair of brothers, Baby Toto and Pietro, sons of different mothers, live stealing suitcases at the Termini Station in Rome. After a theft they discover that the stolen suitcase they got from an apparent sweet old lady actually contains a corpse. In an attempt to discard the suitcase they mistakenly exchange it with the one of two German hitchhikers, Helga and Inga. Forced to retrieve the "corpus delicti" they are discovered by Count Mischa who blackmail them: in exchange for his silence with the police, they will help him to kill his rich wife. After killing the woman, and following a binge of marjuana mistaken for lettuce by the brothers, Baby Toto will turn into a sadist serial killer. After killing the Count and a half-dozen people, he will soon start torturing his brother.