Ahh man, you don't want anyone to build it up bro. I want to say just go in with a blank canvass.
Bogart and his partner are P.I's and take on a case from a woman. The partner gets killed and Bogart then ends up having to find out who killed him and why. In the midst of it all is the Maltese Falcon, a rare precious artefact which everyone is after including a bloke called the Fat Man. That's about as much as you need to know.
The script is brilliant but the real gem of the film is the dialogue, especially Bogart's. The last scene between him and the femme fatale. It's lyrical genius.
Just watch it fgs