United States Marshal Clay Shannon is sent by the territorial governor to investigate apparent attempts to stop the progress of a railroad being driven through the high mountains. The railroad, whose successful completion will mean the joining together of vast regions of the American West, is being subjected to brutal acts of sabotage that threaten its very existence, and Shannon's mission is to find those responsible and end the threat. The quest takes Shannon through brawling railroad camps, where workers of many nations form a violent and often mysterious world where danger lurks for Shannon at every turn, and in every shadow. Here, in this strange new place, Shannon meets many strange new people - a crippled railroad mogul and his contentious family, rowdy railroad workers spoiling for a fight, an enigmatic Chinese doctor, and many others - some friend, some foe, and all a challenge for a lone lawman striving against the odds to solve a puzzle that includes mystery, conspiracy, and murder.