Nocturne (1946) is a full-on film noir moody mystery melodrama, produced by long-time Alfred Hitchcock associate Joan Harrison.
Within the excellent opening photography, we witness rakish Hollywood composer (Edward Ashley) dropping dead in his swanky Hollywood house.
The film noir police force think it's a straight up suicide, but maverick lieutenant hero Joe Warne (played by George Raft) suspects murder.
With no hanging about, Warne discovers that this Hollywood composer has broken the hearts of at least ten women in recent years, offering motive for murder aplenty.
The main suspect is Frances Ransom (played by Lynn Bari), who may or may not have been avenging her sister, the nightclub thrush Carol Page (Virginia Huston).
Pursuing the case with enough firm diligence to get him at one stage thrown off the police force, determined copper Joe Warne of course refuses to give up.
There is a hint here of a sub-genre that would become larger by far as the years passed, the dark side of Hollywood as film noir, which remained popular as much among the community itself, as it was with the theatre-visiting public. Hollywood loves to film itself, murdering itself. In that glorious, glamourous heart, there is always a corrupting influence to be found.