Stealthy Spies, secret weapons, and special missions are just some of the mysteries uncovered in this new series. Each book focuses on lesser-known aspects of history using illustrations, photographs, and activities. Crack open secret files and read about spy trees, bird bombs, famous spies, and more. Did you know George Washington had his own secret agents and hired pirates to fight the British? Buy the entire set of 6 and save. (listed separately)