A stranger named Dunbar comes to the town of Winsome, on the plains of Wyoming, in the 1890's. He goes to work at the Little Six ranch and begins to look into the affairs of Tut Whipple, a water project developer. The investigation starts small, with the tracking down of stolen beef but extends to the disappearance of a young girl named Annie Mora. Dunbar probes here and there, developing an acquaintance with Whipple's wife and an interest in a dam and reservoir Whipple built near the town. Whipple's men come after Dunbar, first with fists and then with guns, until Whipple can no longer avoid a showdown on the dark prairie.