U.S. Marshal Earl Kroeber had barely arrived in Brownsville, Colorado, when the man who had summoned him there was murdered. Ned Brickhill, editor of the "Clarion," had written to Kroeber, a former Texas Ranger, to seek his aid in investigating the bizarre robbery of the Silver Angel Mine, in which an entire wagonload of gold ore had seemingly vanished into thin air.
The ore wagon, bound for the U.S. Mint in Denver, had been hijacked by six armed men who escaped through Sweeney Pass north of Brownsville. Despite the assistance of a contingent of cavalry from Fort MacArthur and Indian trackers, Sheriff Tustin had been unable to follow the tracks through Piute Gorge, where the trail dead-ended in a box canyon against chalky cliffs. No further outside assistance had been requested until Brickhill's letter to Kroeber.
Brickhill had hinted at collusion between Sheriff Tustin and the robbers, but Tustin's attitude toward Kroeber was cordial compared with the open animosity showed him by many of the townspeople. Only Anne Brickhill, the newspaperman's widow, was staunchly on his side, and her loyalty and her loveliness disturbed Kroeber, for they made the matter personal.
Since no one else seemed willing or able to do so, Kroeber decided that it was up to him to solve the robbery and he took slim comfort from the knowledge that someone in Brownsville figured he had enough chance of doing it to want him dead."