Maki, a porter at the Sakura Hotel, finds a body in Room No. 2 and picks up a piece of paper on which is written "one-third of the key", also the part of a key. From a newspaper he learns that the dead man is an official who has been detained as a suspect in a bribery case involving 150,000,000 yen and that another suspect named Matsunaga is still in custody. Maki realizes that if he can obtain the other two-thirds of the key, he will be a multi-millionaire.

Ryōji Hayama
Maki

Mihoko Inagaki
Akiko

Yōko Minamida
Takako

Hiroshi Nihon'yanagi
Matsunaga

Hiroshi Kondō
Hachirô

Kaku Takashina
Kabu

Akira Ōizumi
Nishi

Hiroshi Hijikata
Onoda
Fumio Ōmachi
Takeuchi
Tatsuo Matsushita
Miyaoka

Zenji Yamada
Suzuki

Nobuo Kawakami

Zenpei Saga
Yoshimitsu
Mieko Hirooka
Michie Yokota

Fudeko Tanaka
Michie's mother Toyo