One evening in Tokyo, air traffic controllers detect an unknown flying object and send two aircraft to intercept and identify it. However, the fighters' last message before they crash into each other is 'ryu' - dragon! The whole business has deeply upset Professor Sato Akira, and he calls upon his friend Mortimer, who can always be counted upon for good advice. But before he's even received the invitation, Mortimer is already targeted by men hell bent on getting rid of him.