Before Mantan Moreland gained widespread fame for playing Birmingham Brown in the Charlie Chan films, he made a string of movies with Frankie Darro for the same studio, Monogram. While none of them were exactly brilliant, they generally were well made and enjoyable B-movies. What also is interesting about them is that the pair were usually portrayed as friends....perhaps even equals despite Moreland being black and Darro a white guy. This is most unusual for the early 1940s.
There is a murder at a fancy hotel where Frankie and Jeff (Darro and Moreland) work. Frankie's brother, Tom, is a detective and he asks the pair to keep an eye on a hotel guest as he's a prime suspect. However, the pair are a bit dim and decide to not only keep their eyes open but to actually investigate the case themselves to help out Tom!
The idea of amateurs solving crimes was VERY common in the 1930s and 40s. Often these folks were newspaper men but they could be nearly anyone, as in these B movies the cops were nearly always inept knuckleheads! And, as this type of movie, it's pretty decent and worth seeing. Good acting and a decent script...just like you'd find in the pair's other films.
By the way, although not politically correct, they have Jeff playing craps (a common stereotype of black men during this era), though the white cops end up playing as well....and winning. So, despite the stereotype, the scene ended up being pretty inoffensive to all but the most sensitive of viewers.