Early 1940s, this movie usually gets filed under period Noir. But that's not entirely accurate: yes, it's a mystery, there are criminals and sleazy deals. But "Noir" requires a relatively dark ending, and this one has a lightweight ending that doesn't even particularly fit with the movie. It was frustrating because the dialogue and characters were pretty good, but they were sent off in the service of a plot that didn't make a lot of sense.
Brian Donlevy plays Paul Madvig, a crooked political manipulator. His second in command is Ed Beaumont (Alan Ladd) who's incredibly loyal and the brains of the operation. Which is a problem when Madvig falls for Janet Henry (Veronica Lake) who's the daughter of Reform candidate Ralph Henry (Moroni Olsen). It's more of a problem because Madvig decides to back Ralph Henry because of his infatuation for Janet, against Beaumont's advice. Then Beaumont and Janet fall for each other, and Madvig gets in serious trouble with the local crime boss.
All of which makes sense, but it all stumbles to a surprisingly sunny ending that makes zero sense in relation to the beginning of the movie (or even the middle). Not bad, but quite a mess.