Nichols (no first name was ever given) arrived back in the town founded years before by his family only to learn that it had been taken over by another family, the Ketchams, who functioned basically as a gang. Their matriarch, "Ma" Ketcham (Neva Patterson), soon blackmailed Nichols into serving as the town's sheriff, which carried little real authority (as the Ketchams largely ran things), but considerable danger. Mitch Mitchell (Stuart Margolin) was assigned to be Nichols' deputy, either in spite or because he was none too bright, none too honest, and something of a bully. Nichols (James Garner) soon found a love interest in Ruth (Margot Kidder), a barmaid, who worked for Bertha (Alice Ghostley), the bar's proprietress. Nichols' main concern was not usually law enforcement but rather a way of getting rich with little effort.

The series did not do well in the ratings and was retitled James Garner as Nichols in October 1971 in an attempt to capitalize on the star's popularity. The low ratings also resulted in the decision by the program's producers to kill off the title character. The greedy, but pacifist Nichols was shot down, to be avenged by his identical twin brother Jim Nichols (also portrayed by Garner), who arrived in town and administered justice in a more stereotypical (and it was hoped, more popular) Western fashion. This solution would have made recasting and retitling the program unnecessary while allowing for considerable changes. However, the episode in which the first Nichols was murdered proved to be the final one; before it aired, NBC cancelled the series, rerunning the earlier episodes during the summer of 1972.