When Joe Valachi (Charles Bronson) has a price put on his head by Don Vito Genovese (Lino Ventura), he must take desperate steps to protect himself while in prison. An unsuccessful attempt to slit his throat puts him over the edge to break the sacred code of silence.

Two young men are ineffectual individually, but when together become violent criminals. They break into a wealthy farmer's home only to find that there is nearly no money at the home and murder the entire family to avoid identification. The first part of the film details the search for them, the second, their trial and execution. Taken from the actual events chronicled by Truman Capote in his book.