Nora inu (1949)

During a Tokyo heatwave, Murakami, a rookie police detective, has his fully loaded Colt pistol lifted when riding on a packed public transit bus, he, in a foot chase, unable to catch who he is certain is the perpetrator of the theft. Willing to accept whatever the consequences of what he considers his carelessness, he is determined to locate his gun, which, to him, becomes even more important when it looks like it may have been used in a crime. In his inexperience, he is provided assistance from those on the force more attuned to the pick-pocketing situation in the city and ultimately from veteran Detective Sato, who provides some overall guidance in how to survive emotionally as a detective. In the process, Murakami may have tunnel vision in the guilt he feels, retrieving the gun so that it cannot be used in another violent crime his utmost concern almost at the cost of all else.