After scientists send a signal into space, an alien armada arrives in the Pacific, trapping a fleet of U.S. and Japanese naval ships within a defensive force field during a war games exercise. The immature Lt. Alex Hopper, forced to step up as a commander, leads the remaining naval crews, including his brother's destroyer, to fight the invaders. They must devise a plan to defeat the alien force and destroy their communications before they can call for reinforcements and initiate a full-scale invasion, ultimately using the classic game of Battleship to target the alien mother ship's critical components.
