America in the early twentieth century was rife with threats. Organized crime groups like the Mafia, German spies embedded behind enemy lines ahead of World War I, package bombs sent throughout the country, and the 1920 Wall Street bombing dominated headlines. And one man was tasked with combating these threats.

Born to working-class parents in 1867, Willaim Flynn launched the first antiterrorist program, unraveled a German spy network, and took on the Mob. Dubbed “the bulldog” for his tenacity, Flynn earned a high-profile reputation as one of the most respected, incorruptible, and storied law enforcement officials in the country.

To explore these issues is today’s guest is Jeffrey Simon, author of "The Bulldog Detective: William J. Flynn and America's First War Against the Mafia, Spies, and Terrorists." He takes us back to an era when counterfeiters plagued butcher shops, German spies rode the subway, and anarchists bombed targets across the country, including using a horse-drawn wagon to set off an explosion on Wall Street that, at the time, was the worst terrorist attack ever to occur in America.