A Japanese submarine is lost and the captain of another Japanese sub learns that it was deliberate. It was all to prepare its crew for its true mission, to secretly operate the first Japanese nuclear submarine, The Seabat, in cooperation with the United States. However, things take an unexpected turn when the crew under Capt. Kaieda mutinies and renames the boat, the Yamoto. Now the US and Japan are in a frantic search for the renegade sub while the Captain follows through on his plan that will rock the relations with the two countries to its core.