The basic thrust of the series was that two well-meaning outlaws, Hannibal Heyes (played by Duel) and Kid Curry, a sharp-shooter played by Murphy, wished to go straight. They were promised a pardon by the state governor on the understanding that they stayed out of trouble for a certain length of time.
In order to avoid capture, the two outlaws used the pseudonyms Joshua Smith and Thaddeus Jones. In almost every episode, they would find themselves with an opportunity to help someone, but at the risk of giving away their true identities. They were also being pursued by a detective from Pinkerton's agency.
When Pete Duel died suddenly in 1971 -- a possible suicide -- an attempt was made to continue the series with another actor, Roger Davis, in the role of Heyes/Smith. The series continued for another year, but never regained its initial popularity.