Story of a young woman, Mrs. McBain, who moves from New Orleans to frontier Utah, on the very edge of the American West. She arrives to find her new husband and family slaughtered, but by whom? The prime suspect, coffee-lover Cheyenne, befriends her and offers to go after the real killer, assassin gang leader Frank, in her honor. He is accompanied by Harmonica, a man already on a quest to get even.