Hajime realizes that the killer has been listening to the group via a hidden microphone and uses it to trap the killer who is found to be Eiji Touno. Touno had actually killed Shigeru Kikkawa and disguised the body as himself. Touno wanted revenge on the person with the initials "S.K." who had pushed his sister Keiko away from a full lifeboat during the sinking of the Oriental in a case of the Plank of Carneades...