Toshiro Mifune was his country’s most internationally famous movie star as much as Akira Kurosawa was its director. To honor what would have been the late actor’s ninety-sixth birthday this April Fools’ Day, Japan Society’s “Monthly Classics” offered in 35mm the 1949 Stray Dog/Nora Inu, that director’s first notable work and an early, pre-samurai pre-Shakespeare vehicle for both him and the actor.

Not finding U.S. distribution for nearly a decade and a half and denigrated by its maker as so technical as to be devoid of any “real thought,” the two-hour-two-minute b&w is a police procedural with a different story line and a feel for Tokyo’s post-war deprivation and dog-eat-dog milieu. Legend has it based on an unpublished work by an ex-detective which impressed Kurosawa to write his own unpublished Georges Simenon-influenced novel which in turn became an in effect adapted co-authored screenplay. (Co-writer Ryuzo Kikushima later fell out with the director, as did Mifune.)

Not yet thirty, with matinée idol looks in an innocent face, Mifune is Police Detective Murakami, whose greenness is good-naturedly corrected by everyone else on the force. Indeed, action is set in motion just seconds in, when his .25 caliber Colt automatic is stolen on a packed bus during the summer heat that pervades the film up to the final downpour.

He chases but loses the pickpocket and immediately tenders his resignation in despair and shame. Cooler, experienced heads temper such rashness and prevail upon him to stay on but to consult the Evidence Section’s card catalogue drawers of photos.

With the doggedness and abandon of youth, he pursues the woman whose headshot confirmed her as the one standing beside him on the bus and who, outmaneuvered and worn down by his persistence, refers him to the club Bawda, where a woman of low repute is arrested but at first refuses to cooperate. Using three-and-a-half decades’ worth of beat experience, family man and Section Chief Detective Sato (Takashi Shimura) is more realistic and with cigarettes for added measure worms out names and places.

Disguised as another down-and-outer, an ordinary demobbed soldier, the young detective roams the slums of the capital looking for fences who specialize in stolen weapons. (Filmed in real, potentially dangerous yakuza turf, these scenes mostly show only the pretended soldier’s lower body, which was actually that of chief assistant director Ishiro Honda.)

Going through the long actual footage of a Tokyo Giants-Hawks baseball game, a girlie club chorus routine with poor venal showgirl Harumi Namaki (Keiko Awaji), and the shanty home of the sister of troubled ex-soldier Yusa (Isao Kimura), the older and young detectives track the path of the stolen gun whose bullets have been matched by Ballistics with those used in at least one brutal robbery-murder.

As in many similar films, convolutions grow a bit much, things get confused and confusing, and viewer logic will uncover inconsistencies. There are hints of social consciousness, as in Harumi’s pathetic wishes for the simplest of finery and an escape from poverty and in Murakami’s strained empathy for a culprit whose knapsack was also stolen and who winds up done in alongside him on a hillside. But such are really asides from the main thread, whose resolution depends on the thunderstorm that ends the terrible heat wave and spatters telltale mud on trouser legs.

Like the hero’s white linen suit and newsboy cap, these side touches garnish the trail of the pistol that leads to a lost indigent boy’s affection for a penniless girl. Brought to a conclusion, its lesson enunciated by Sako, the case serves as Murakami’s coming-of-age as a cop.

Over the years, this competent but routine if visually effective detective flick has frequently been styled an early gem. But that verdict is really a backwards judgement in hindsight, reading into it the bona fide masterworks that were to come.

(Released by Janus Films; not rated by MPAA.)