Kenmochi discovers that Captain Takamori and Navigator Wakaouji and were commanding officers on the Oriental cruise ship which sank after colliding with an oil tanker 3 years earlier. They were rivals but the collision ruined both their careers. That night, Wakaouji is poisoned and his body is thrown overboard. They find a suicide note in Morse code saying he has terminal cancer and that he killed Takamori and Mizuzaki...