A Turning to Hell (1959)

Original title: 地獄の曲り角

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.