Following the Bay of Pigs disaster, and a second crisis in Europe resulting in the deadly grey reality of the Berlin Wall, an over-confident Nikita Khrushchev decides to further test what the Soviets see as a weak and vacillating Kennedy administration. As US reconnaissance overflights of Cuba resume after a hiatus following the events at Playa Giron, analysts are shocked to discover rings of Russian-made surface-to-air missile installations. While these themselves pose no threat to the United States, the installations follow the classic designs used by the Soviets to protect important ground installations.
Then they see them: Russian medium-range, nuclear-tipped missiles capable of striking the entire East Coast. More are on the way from Russia, lashed to the decks of Soviet transports. Announcing an outright blockade of Cuba would be recognized as an act of war, so President Kennedy employs the Soviet tactic of linguistic sophistry and announces a "quarantine zone." As US Navy warships move to intercept the incoming missiles, the fate of the world hangs in the balance -- and is ultimately in the hands of a single man, not in either the White House or the Kremlin, but deep beneath the waves at the edge of the quarantine zone.