Blackmail (1947)
The character "Dan Turner, Hollywood Detective" was pretty popular in the pulp magazines of the 1930's and 1940's. This is his only theatrical appearance, although he would show up many years later in a made-for-TV movie (and, apparently, the pilot for an unsold series) called, logically enough, Dan Turner, Hollywood Detective (AKA The Raven Red Kiss-Off on video, which may be the most hardboiled title I've ever seen.)
Anyway, this is an entertaining little B private eye yarn. Turner gets hired by a wealthy stage-and-radio producer type, who relates his problem in flashback. It seems that he won a ton of money at a gambling joint, then ran into an old flame (as fits tradition, she's a nightclub singer) who doesn't seem to resent the fact that he dumped her and failed to get her the radio spot he promised. She gives him a drink that knocks him out, then blackmails him with photographs. (We don't see these, or get a clue what they show, but to be worth fifty thousand bucks -- a price which keeps going up during the course of the film -- they must be pretty racy for 1947.) Then the dame fell out of a hotel window -- or was pushed -- and the rich guy looks like the best suspect.
Out of the flashback, the dame's partner in blackmail shows up, has the first of three long and really impressive fistfights we'll see in a film that lasts just over an hour -- Republic Studios did a bunch of serials, too, so had great stuntmen -- with Turner and runs off. Somebody we don't see shoots the guy dead, and he lands in the wealthy guy's pool. The rich fellow stupidly picks up the discarded gun, making him another prime homicide suspect. His current girlfriend shows up, and with the help of a chauffeur with a phony French accent, the body get hidden to protect her man.
The movie has just barely begun at this point, and it gets a lot more complicated. The screenplay is full of wisecracks, maybe the most smart aleck remarks per minute in any movie I've ever seen. You'll figure out who's behind the blackmail and murders, but it's still a lot of fun.