In the summer of 1914, New York City Police captain Tom Tunney is preoccupied by Manhattan's raging gang rivalries and has little idea that, halfway around the world, a much more ominous threat to the city is brewing. As Germany teeters on the brink of war, its ambassador to the United States is given instructions to find and finance a team of undercover saboteurs who can bring America to its knees before it has a chance to enter the conflict on the side of the Allies.

Overwhelmed and undermatched, Tunney's small squad of cops was the David to Germany's Goliath, the operatives of which included military officers, a germ warfare expert, a gifted Harvard professor, a bomb technician, and a document forger. As explosions leveled munitions plants and destroyed cargo ships, particularly in and around New York City, panicked officials talked about rogue activists and anarchists—but it was Tunney who suspected that these incidents were part of something bigger and became determined to bring down the culprits.

Through meticulous research—and enhanced by more than fifty images sourced from global archives—Blum deftly reconstructs an enthralling, vividly detailed saga of subterfuge, bravery, and the birth of Homeland Security.