Lt. Thomas Mullin, retired against his will but almost glad to be free of the searing dusty desert around Fort Davis. A hard life in a hard place for a black man in a white man's cavalry. The US Cavalry was glad to be rid of him, too .. until a US Senator's son disappears in the desert and someone realizes that Mullin was the best tracker around. Mullin quickly discovers that quite a few travelers and cowboys have recently disappeared without a trace in the exact same area. Here was a problem that no self-respecting reader of the Strand Magazine could ignore. No devotee as religious as Mullin could pass by a mystery as strange as this. Why, it would curl the hair of Sherlock Holmes himself