Stray Dog (1949)

Murakami (Toshirô Mifune) is a young and inexperienced detective on the Tokyo police force. While riding a crowded bus on a hot summer day, he discovers that his gun has been stolen out of its holster.

Reluctant to lose face by reporting the gun missing, Murakami first dives alone into the depths of postwar Tokyo's poverty-stricken slums and criminal underworld, but when the missing gun is implicated in a crime spree, a more experienced detective (Takashi Shimura) lends his expertise.