Donover Valley was a rich and fertile rangeland, and old Bob Craig's Question Mark spread, with its cattle-teeming acres, was the pride of Donover. But two recent developments were bothering the Question Mark owner: the encroachments of the nesters in the Valley, and the large-scale rustling which was depleting the herds.Craig was inclined to blame the homesteaders for the beef raids, but his foreman Ray Evart suspected some more powerful and more sinister figure was responsible.