B-movies were short and relatively low-budgeted films intended as a second film in a double-feature. Usually, there was an A-movie, some more prestigious and larger-budgeted film as well as the B....along with various shorts (such as a cartoon and/or a news reel) shown at most theaters during this era. Many of them were made by small studios like Republic or Monogram and many more were made by practically microscopic studios that actually didn't own their own studio space but rented it from a larger studio and filmed mostly at night. But what many folks don't know is that the biggest studios ALSO made Bs, and "The Longest Night" is clearly a B...and it is from MGM...the largest and fanciest studio of the era.
So why is "The Longest Night" a B? Well, at only a paltry 51 minutes, this alone would make it a B-movie. But it's also a fancy B (almost a B+ film if there was such a thing), since it's cast has some A-list actors, such as Robert Young who is in the lead.
"The Longest Night" is a murder mystery. Apart from westerns this was probably the most common genre for Bs. A few of these mysteries were very good. Most, sadly, are filled with cliches and are very formulaic. Despite "The Longest Night" being a higher-budgeted B from MGM, I'd place it in the latter category...being mostly formulaic and cliched.
What are some of these cliches and formulas? Well, in this case you have the typical idiot cop investigating (Sidney Toler is particularly one-dimensional here), his even stupider sidekick (Ted Healy is practically sub-human in his stupidity and uselessness), a smart civilian who for no discernible reason is practically Sherlock Holmes (Robert Young) as well as predictable scenes, such as one where someone says "I didn't kill her, but I'll tell you who did..."....and a shot rings out and kills them!! In other words, no matter how enjoyable all this is, it's also predictable and a bit silly. This clearly is NOT a thinking person's mystery and it obviously was hastily written. On the plus side, however, the cinematography is unusually good and the film is slick looking and enjoyable. Overall, a very mixed bag.