In December 1974, the crew of the cancelled Apollo 18 mission is informed that it will now proceed as a top secret United States Department of Defense (DoD) mission disguised as a satellite launch. Commander (United States) Nathan Walker, Lieutenant colonel (United States) John Grey, and Captain (United States O-6) Ben Anderson are launched toward the Moon to place detectors to alert the United States of any impending ICBM attacks from the Soviet Union.