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 his branch brought to justice reads like a Who’s Who of mid-twentieth-century crime and crooked politics: Boss Tom Pendergast in Kansas City, the Huey Long gang in Louisiana, Enoch “Nucky” Johnson in Atlantic City, Morris Kleinman of Cleveland’s Mayfield Road gang, and Leon Gleckman, the “Al Capone of St. Paul. The Irey-led investigation also resulted in the prosecution of businessman and publisher Moses L. Annenberg, a cagey racketeer who was once one of the nation's wealthiest figures.Leading his own investigation into the emergence of America’s criminal underworld, Robert G. Folsom successfully places Irey in his rightful place as the twentieth century’s greatest law enforcement figure. It was shortly after the era of Prohibition—with its rampant corruption, organized crime, and compromised officials—that Irey truly made his mark. While Attorney General Homer Cummings sent Hoover and the G-Men after bank robbers, Irey and his T-Men were cracking down on New York racketeers such as Waxey Gordon and Dutch Schultz, who amassed more illegal cash in one week than celebrity bandits like John Dillinger stole during their entire careers. Irey’s work with Manhattan D.A. Tom Dewey—including the use of investigative accountants–led to the imprisonment of Charles “Lucky” Luciano, the Mafia’s boss of bosses. A few years later, the Irey-led investigation of the Hollywood stagehands’ union extortion plot would result in the first-ever takedown of a Mafia-aligned group—fifty years before U.S. Attorney Rudolph Giuliani went after the Mafia’s Five Families. In its detailed coverage of Irey and his hard-won battles against crime, reveals how the forces of good can overtake the corrupt.