New York Times bestselling author Neal Bascomb delivers a taut and timely forgotten history—equal parts Peaky Blinders and The Departed—of the Molly Maguires, the Irish secret society that terrorized Gilded Age America, and the young immigrant detective who went undercover, alone, to bring them down. The first true-crime saga of the robber-baron age.

Pennsylvania, 1873. Franklin B. Gowen—thirty-five, silver-tongued, ruthless—is president of the Philadelphia & Reading Railroad and master of the anthracite coal that fires the nation. Only a miners’ union and its shadowy marshal arm, the Molly Maguires, stand in the way of his absolute control. For years, this secret Irish gang operating in the fearsome coal mountains has sabotaged the industry’s mines of “black gold” and brutally killed its bosses. Gowen hires Allan Pinkerton’s famed detective agency to destroy them, convinced that local law enforcement is too weak—and too corrupt—to win the fight.

Enter James McParlan, only a few years removed from Ireland. Pinkerton sends this rookie detective to infiltrate the Molly Maguires, root out its leadership, and end the chaos. It is a daunting mission, but with a mix of bravado, fisticuffs, and well-spun yarns, he enters their ranks. What begins as a singular assignment becomes a multi-year operation that will ultimately rivet the nation. But behind the blood-curdling headlines lies a more complicated truth. By his avarice and monopolistic obsession, Gowen provokes exactly the kind of violence among the starved, destitute miners that he claims to be ending. McParlan finds himself caught in the middle of this industrial age war, his nerves and identity fraying as his life—and soul—hang in the balance.

Based on the real-life events that inspired Sir Arthur Conan Doyle’s final Sherlock Holmes mystery, Over Wicked Mountain is an American epic—and a story for our own age. It is an unsparing portrait of what justice looks like when the gap between rich and poor has grown too wide, and what happens when vengeance becomes the last resort of the oppressed.