War is a time of secrets. Advances in technology during the height of World War II provide new methods for spies to keep secrets, steal information, and destroy enemy plans. You're about to go under cover. Will you: Become a resistance fighter in Denmark, revealing Germany's false claims of protection? Work as a "double cross" agent, pledging loyalty to one country but actually spying for another? Join the U.S. Office of Strategic Services, shuttling...