This was an interesting, though sometimes turgid book--lots of repetition, dull in some places,and violent in others. Jack McKenna--his undercover name--went anonymously to join this violent group of miners, and remained for many years, despite suffering from a recurring illness and other maladies. He did not have an easy time of it--trying to stay alive, but managed to sneak out a lot of information for the Pinkerton organization.