Wow, lots of crime, corruption, killing and, of course, quaffing (the hard stuff).
So, the Continental Op goes to a small town, where his summoner is killed before he can even meet with him. The summoner's father, who essentially owns the town asks the Continental Op to clean up the corruption (then off and on changes his mind). The clean-up essentially involves getting all the various gangsters to kill each other.
I suppose this is a good yarn, and a classic example of its genre. I have issues with a book who's protagonist is essentially anonymous. I'd read some Continental Op stories before and had the same feeling. Much better, IMHO is Chandler's Philip Marlow. Both Chandler and Hammett feature private detectives midst a background of crime, corruption and killing, but somehow having a "known" protagonist is more satisfying.