As the first chief of the Special Intelligence Unit at the Treasury Department, Elmer L. Irey accomplished what J. Edgar Hoover wouldn't and Eliot Ness couldn't. From the 1920s through the 1940s, he headed the investigations that led to the prosecution of the ruthless, murderous bosses who ruled American cities without fear of the law. Irey's takedown of Al Capone is still the landmark law enforcement achievement in U.S. history. Those whom Irey and...