Russian sleeper agents left over from the Cold War take over an Alaskan radar station when they think a strategic nuclear attack from Russia has been launched at the United States. Frank Trask, an engineer at the site, and Ellen Gain, a covert CIA agent, race to stop the Russian agents while trying to survive the extreme elements on the Aleutian Island of Shemya. The two hook up with two other survivors of the Russian agents' vicious attack on the island personnel. Elverson, a security guard, and Vaughan, a personnel employee, join Trask and Gain in trying to figure out why their island has been taken over by hostile forces. Trask struggles with inner demons, his excessive drinking and is haunted by his past as a sniper in Vietnam. He comes to the sudden conclusion that one of their group is a traitor, waiting to betray them at any time. Meanwhile U.S. Marines are sent to Shemya when communications are broken between the island and NORAD. A U.S. attack submarine is also sent into the area and tracks a Russian submarine whose intent is unknown. The Russian sub deploys a Spetsnaz team onto the island. All these forces converge for one final battle at the top of the world.