In 1987 the Soviet Union launched a secret mission to place a nuclear missile base on Cruithne, a small planetary rock whose orbit comes close to the Earth once every year. The unmanned base was equipped with a receiver that, upon each approach to earth, would listen for a message telling it "The USSR is alive and well." Should this message fail to be received, the missiles would launch, raining nuclear destruction onto the United States.

For the decades following the fall of the Soviet Union, Pavel Durov, the former Chief of Communications for the Cruithne project, has made an annual trek to a remote mountain in Kyrgyzstan, from which he has transmitted the message. The years pass, but Pavel can find no one he trusts to take over the responsibility. There are many who would like to see the United States annihilated.

In present day, Ethan Morris receives a package containing a letter informing him that his old friend Pavel has died. Included in the package is a mysterious notebook, detailing the Cruithne mission and the need for the annual transmission. Faced with a skeptical American government, Ethan and his wife Brooklynn travel to Kyrgyzstan, where they must locate the transmitter and obtain the code that must be sent. They face deadly opposition from Russians, terrorists, and other enemies. Like Pavel, they must determine who they can trust to help them, before the countdown ends and the missiles launch.