AllMovie

The Seaview is drawn to a mysterious undersea formation, where they discover a German-built underwater base -- from the Nazi era. Also present are two men (John Van Dreelan, Jan Merlin) in suspended animation, now revived and just as dedicated to victory for the Third Reich as they were in 1945. While Nelson and Crane struggle to repair the submarine, which has been damaged by a mine, the two revived Nazis begin making plans to attack the capital cities of the Allied nations, but not with their antiquated V-weapons -- instead, they're going to use the Seaview's nuclear missiles.