As I remember Nichols, he rides into town after retiring as a sergeant in the army...early 1900's. He rides in on an Indian motorcycle. He winds up as sheriff, with Stuart Margolin as his deputy, and the Ketchum's (Ma and son) as the "bad guys...kinda". Margo Kidder is his girl...sorta. He never uses his gun; he talks people out of causing trouble. He was Maverick. And then the final episode. He is killed before the credits run in the last episode while trying to keep two old koots from killing each other. Some time passes in the town...his twin brother rides into town. It is the James Garner that plays Wyatt Earp in the movie (mean...never smiles....bad attitude). He cleans up the town, rights the wrongs, and rides out of town on his brother's Indian. Great ending. Great show.
