When several ships transporting goods across the North Pole vanish, Cmdr. Wendover (Dick Foran) is charged to find the cause. Along with Lt. Cmdr. "Reef" Holloway (Arthur Franz), Wendover takes his submarine and crew to the location of the disappearances, where they discover an underwater saucer. After realizing that the ship is an alien spacecraft, they attack, but without success. It is left to Holloway and Dr. Neilson (Brett Halsey) to man a smaller submarine and board the alien ship.