Pinkerton's somewhat fictitious, self-aggrandizing account of his agent's infiltration of Irish miners in Pennsylvania. The labor wars between the Irish immigrant miners and the mine bosses was occasionally violent, resulting in murders and labor strikes. In reality the work of Pinkerton agent James McPartland at the behest of mining boss Franklin Gowen resulted in mob justice against the Mollies. The true story is much more complicated than Pinkerton would have you believe, as Gowen's motive was to crush the formation of a labor union amongst the miners, while he was buying up mines in the area in order to corner the anthracite coal market there. Nonetheless, this book cemented Pinkerton's reputation and resulted in a string of best selling sensationalist "true detective" stories, assuring the name of Pinkerton as one permanently associated with ace detective work. But remember that the Pinkertons were frequently hired by big business as a sort of private police force using tactics that the justice system might well have found questionable.