Dunbar, working on a ranch in the Niobrara country in Wyoming, connects the death of a hardscrabble homesteader with the death of an old horse trader some fifteen years earlier. As Dunbar goes to work on a corral project in town and then on fall roundup, more murders take place-a wandering drunk who had picked up gossip in an alehouse, and then the proprietor of that alehouse. People who know too much are being silenced. An eccentric resident tells Dunbar of an ancient crime on Old Woman Creek, where a sheepherder was killed and his partner escaped. In a final showdown at the new shipping pens, Dunbar brings forth the witnesses, and a shootout erupts, with Dunbar bringing justice to the Niobrara country.