After a North Korean nuclear missile test goes wrong, the American submarine USS ''Lansing'' is cut off from communications. Detecting radioactivity in the air and believing the world to be at nuclear war, the executive officer takes command of the ship from the Captain (naval) and prepares to fire the submarine's nuclear missiles at targets in Russia. Some members of the crew do not believe they are at war and help the captain take back control of the ship. Meanwhile, a second American submarine is sent to hunt down and destroy the ''Lansing'' before it can start a real war.