The Nightriders(Wells Fargo Trail‪)‬

Popular author Jim Walker thrills fans with the riveting adventures of Wells Fargo agent Zach Cobb. When a rash of gold robberies breaks out in California, Zach is dispatched to conduct an undercover investigation. He'll need to work fast, for an angered vigilante group is interpreting the law its own way, and innocent people are being hanged. With his strong sense of moral justice and some help from a few honest friends, Zach will give the thieves more than they bargained for.