Guy Williams is Damon, a rather rouge character who steals and connives for a living, but happens to believe that all men are brothers. Don Burnett is Pythias who has the same beliefs, but a much different lifestyle.
Pythias is arrested for crimes against the King of Syracuse, Dionysus and sentenced to death. Damon and Pythias strike a deal with the King an Damon takes the place of Pythias while he travels to get his affairs in order.
The King agrees but then does everything in his power to kill Pythias before he can return. This is a pretty standard drama, but it does hold your interest.