In the turn-of-the century Texas town of Cottonwood Springs, marshal Frank Patch is an old-style lawman in a town determined to become modern. When he kills drunken Luke Mills in self-defense, the town leaders decide it's time for a change. That ask for Patch's resignation, but he refuses on the basis that the town, on hiring him, had promised him the job for as long as he wanted it. Afraid for the town's future and even more afraid of the fact that Marshal Patch knows all the town's dark secrets, the city fathers decide that old-style violence is the only way to rid themselves of the unwanted lawman.

The pilot film for the long-run series introduced the kindly small-town general practitioner who, following a mild coronary, grudgingly brings in an independent, motorcycling young associate to help share his workload. Welby's lady friend and his family, part of the plot of this movie, were written out of the subsequent series, with only his medical sidekick, Steven Kiley, and their secretary/nurse, Consuelo, remaining as regulars.

Carl Dixon decides to quit school and enlist in the Army, even though he's already run afoul of the law as a Vietnam protestor. It is our hero's intention to use love, rather than bullets, to combat the Viet Cong. Needless to say, his idealism is no match for the harsher realities of war.