I agree with everything you said, enjoy this, and find the story and depicted investigation to be interesting, and the performances good.

I've seen, elsewhere, that some noir enthusiasts dismiss this movie as not being "noir enough", or as being too slow-paced, though I watch and enjoy this for the good little movie that it is in its own right, not for what it's not.

What a scenes-stealing performance by Elsa Lanchester as the landlady!

A few random observations: This was the first Hollywood movie filmed in Boston, and it foreshadows future TV police procedurals such as CSI. It was also one of the earlier, though by no means earliest, films to star a hispanic actor. I lived in the Boston area for 28 years, so all of the location shots were familiar to me, and rather nostalgic. Some of it has changed, but much of it has not. Fortunately, much of the city escaped the early 1960s urban renewal that replaced places like the quaint, Victorian-architectural Scollay Square with the ugly, Brutalist architecture (yes, it's a real architectural term) monstrosity called Govt. Center.