At about the same time as lwami, president of a Tokyo company is murdered by an unknown assailant, it happens that an urgent call has been received from an airline company's office on remote Hachijo Island for a special serum. A Cessna aircraft which has been chartered by a man named Ohashi takes off for the island with the serum piloted by Ishida. But when airborne, Ohashi, who is the murderer of lwami, holds up Ishida at gunpoint and orders him to land on a small island west of Hachijo where a ship is waiting to take him to Hong Kong...