An American submarine, USS Tampa Bay, disappears as it passes through a Russian submarine in the Arctic Ocean. Admiral John Fisk sends another submarine, USS Arkansas, under the command of the newly-promoted commander, Joe Glass, to investigate. At the same time, a Navy SEAL unit under the command of Lieutenant Bill Beaman is sent to discreetly observe a Russian naval base, but their mission is complicated when Martinelli, one of the new recruits of the unit, has a problem severe.
When they arrive at the naval base, they observe how Defense Minister Dmitry Durov heads a coup and takes the Russian president, Zakarin, as a prisoner, and realizes that Durov has the intention of launching a war. Meanwhile, Arkansas discovers the lost American submarine, and also discovers another failed Russian submarine, and the damages suggest that an interior sabotage would have occurred rather than an external attack.
They are then attacked by another Russian submarine that has hidden under an iceberg, but Glass manages to destroy the enemy ship and saves Russian survivors from the wreck, including Captain Sergei Andropov. Back to the base, the US government is learning about the Russian coup. Admiral Charles Donnegan recommends preparing for war while Fisk suggests that Arkansas be sent to take over Zakarin that has been saved in the meantime. Glass manages to persuade reluctant Andropov to help them, and with his knowledge of the mined field surrounding the base, Glass reaches the base without being detected.