Plot

An American soldier learns that he is one of five people around the world who are separately sealed underground for a year and are charged with preventing Earth's self-destruction as the world awaits a possible invasion by aliens.

Ben Conklin is a last-minute replacement for a long-term isolation assignment. He's advised by General James Eiger that, some time ago, long range probes identified an alien force heading directly for Earth. In the event they should lose any battle with the aliens, they have arranged for a self-destruct mechanism to destroy all life on the planet. The system will automatically fire, giving Conklin 30 seconds to hit the kill switch. Eiger tells him that if they succeed, they will dig him out in about a year's time; if they don't appear, he should assume the worst. Conklin learns that there are four others in different locations around the world who can also stop the doomsday device from firing. For most of the year, not much happens. Conklin becomes friendly with Katya Rubinov, but when his counterparts start to die, he considers letting the timer count down.—garykmcd

When world leaders discover aliens en route to earth, four people around the world are stationed on "dead men switches" deep underground in bunkers. Periodically, a doomsday weapon activates requiring one of the four to deactivate it. The aliens claim to be friendly, but their motives are unclear.