From the American Film Institute:
"In New York, a man is killed and robbed of $300,000 on his way to a bank night depository. A year later, as Los Angeles police detective Calhoun Bruner is walking home one night, he happens upon a drug store burglary in process, shoots one of the two burglars and arrests the other. The police then discover that some of the money the burglar took is "hot" and from the New York robbery, for which no arrests have been made. When Captain Michaels asks the drug store owner where a particular $50 bill came from, the druggist tells them that he received it, as payment for filling a prescription, from a bartender at a local night club. The next day, Cal and his colleague, Jack Farnham, interview the bartender, who tells them that he borrowed the bill from Lilli Marlowe, a singer who works at the club. Unfortunately, Lilli can only give a very vague description of the drunk who gave her the bill. After more bills show up at the Hollywood Race Track, Michaels asks Lilli to go on a stakeout with Cal and Jack in the hope that she may recognize the man. Although several days at the track prove fruitless, a romance develops between Cal and Lilli. On yet another day at the track, while checking cars leaving the parking lot, Lilli spots the man and Cal and Jack chase after him, but the fugitive's car crashes off the road and he is killed. In the wreck, Cal and Jack find a metal box full of money and Cal takes four wads of bills."
And that's where things really get interesting. In this film, written by and starring Ida Lupino as Lilli, and directed by Don Siegel (who went on to direct THE LINEUP, the remake of THE KILLERS and DIRTY HARRY, among others), Cal Bruner is our noir protagonist. He falls hard for Lilli and sees her noticing nice things like diamond bracelets. He wants to get those things for her, and figures he can pull his partner in, since he's having money troubles with a wife and kid. The style is not overt, and Lupino's script can sometimes make 75 minutes seem like a long time, but when it gets going, it's a good look into how one man can talk himself into a downward spiral and take it "straight down the line."
edit: Also, the film ends with this great voice-over narration: "A policeman, unlike most men, lives close to evil and violence. He can, like all men, make his own private hell. The good pass through it with minor burns. The evil stumble and fall, and die in strange places." Awesome!