S1·E19 The Bounty Hunter

When a Mexican bounty hunter shows up in Bordertown, Jack is instantly suspicious, suspecting that the Mexican has actually come for him. When he and Marie are jailed by the bounty hunter, Jack confesses his secret past to Marie, revealing that his wife and daughter had been murdered by Don Carlos, a wealthy Mexican landowner who had been trying to drive Jack and his family from their land. In the ensuing fight, Jack had killed the Mexican's son. Seeking revenge, Don Carlos wants Jack delivered to him alive, but his bounty hunter has no problem with using Marie as a pawn to control him.