The story is about Dwight "Bucky" Bleichart. Bucky - so named for his buck teeth, is a ex-champion light heavyweight boxer, who is now employed by the LAPD. Sometime in 44/45 there were a series of riots in LA between soldiers/sailors/marines on leave and mexican-american gangs - they were known as the 'Zoot suit riots'. Bucky is involved in one and the violence disgusts him and he tries to get out of it (for a boxer, Bucky hates violence). He encounters another cop taking out 4 or 5 guys who are beating up some hispanic guy and recognizes Leland "Lee" Blanchard, a rival boxer, 36-0-0 and now a cop. Lee explains to Bucky that the soldiers were beating up 'his collar' - he works for warrants division and he's just there to pick up a guy for outstanding warrant (i.e. he's not saving the guy for any humanitarian reasons). Warrants is the division to be in - that's where all the real copwork is - picking up the bad guys. The two of them stay out of the rest of the riots.

Flash forward a year or so, 1946. Bucky is approached by a prosecutor named Ellis Loew and the police chief. They want a proposition to pass in the election that will give the police department a lot more money, but the LAPD has a really bad reputation, so it's unlikely it will pass. They've come up with this idea to put together this fight card called Mr Fire vs Mr Ice and have the press write up some great story about these two ex-boxers who are now famous cops. Lee has already gained notoriety when he busted a couple of bank robbers in '39. One of them, Bobby De Witt, went to San Quentin for 10 to life, and the rumour is that his gal was the one that snitched on the heist. She's now living with Lee, but they are not married which is against departmental regulations. Loew has an offer that neither boxer can refuse - fight and the winner gets what they want from the department - for Bucky that's a job in warrants, for Lee, no reprisals on his living situation.

As Bucky prepares for the fight, we learn that he has a senile father that he needs to take care of. He really wants to go to warrants, but he needs to take care of his dad, so he goes and bets on himself to lose, and plans to take a dive and get a load of money to set his dad up in a good home. In the fight, Bucky has a change of mind and decides he can't lose on purpose - he can't play dirty. He fights full out but it doesn't matter because Lee still knocks his clock. This part of the film is long, but it's to set up Bucky's character, he considers going 'bad' all the time, but he can't do it, he's very ethically inclined. He loses warrants, but he does get his money to set his dad up. In the end, the event was a huge success and the proposition goes through. Loew is so pleased, he gives Bucky the job in warrants and Lee and Bucky are partners

Lee and Bucky become best friends and Kay, the girl that Lee 'rescued' from De Witt comes into the picture. Bucky doesn't understand the relationship between Lee and Kay as she tells him they do not sleep together. But they have a solid threesome, right to the end of 1946.

In January, 1947, Lee and Bucky are tailing a real badass named Junior Nash. They are staking out a building at the edge of town, near some new subdivisions, they see a few people walk in the building when Lee says 'get down' and there is a shoot out - there are four dead guys, but Bucky is convinced Lee saved his life! Bucky learns that one of the guys they killed - Baxter finch (?) - was a one-time informant for Lee. Before Bucky can ask about this, there is a loud commotion a block or so away - a naked mutilated body has been found. They go to investigate

The body is gruesome - cut in two, the blood completely drained out, all the internal organs missing. What killed her was either being beaten to death by a baseball bat, or choked on her own blood - the killer had cut her mouth ear to ear in a death grin. The body was just dumped on the side of the road. The press is going crazy - she was a pretty, young girl who was known for wearing all black, and the papers dubbed her 'The Black Dahlia'. Her real name was Elizabeth Short. She was played up as being a sweet young innocent actress, but the truth was, she was a liar, a very bad actress that spent more time on the casting couch than on camera, and would use men for money. But the case was big, so Lee and Bucky are pulled off warrants (and Junior Nash) and onto homicides. Lee is obsessive about the Black Dahlia and refused to believe she was anything else but an innocent. Bucky wants to go after Junior Nash before he kills someone else, and thinks that Liz Smart (aka Beth, Betty, etc) was a ho and got what was coming to her But he's not allowed to go back to warrants - the head of homicides - Russ Millard - really likes him and thinks he's a 'smart penny'.

While investigating the case, Bucky interviews several residents of the flophouses that Liz stayed at before her death. He discovered that she spent a lot of time with a girl named Lorna, who was underage, and they used to fleece men for their money. One friend saw them together with a woman who looked very manly (a lesbian), so Bucky decideds to follow that angle. Meanwhile, Lee is becoming unhinged, he's taking poppers and he's going nuts over the dead girl, taking home copies of police files that he shouldn't have. He's becoming unreliable and Bucky finds out that Bobby DeWitt, the man behind the robbery he busted and the one who beat up Kay before Lee rescued her, is getting out in a week. Bucky is sure that Lee is upset because Dewitt will be coming after Kay, and he wants to protect her. Kay is getting upset with Lee's behaviour and kicks him out of the house so he goes to Bucky's dad's apt to do work on the case - only for a week. He asks Bucky to take care of Kay. Kay tells Bucky that Lee is strung out becuase his sister was murdered at 15yrs old. Bucky thinks this and the dewitt thing is making his best friend crazy, so he lets him be.

Bucky follows up on the lesbian lead by going to a few lesbian bars. He doesn't get much info, but he does notice a very rich, good looking woman leave the bar when she notices him asking questions. He follows her. Turns out her name is Madeleine Cathcart Linscott, daughter of Emmett Linscott, a famous developer. Bucky is attracted and disgusted by her at the same time. He confronts her, she says she doesn't want anyone to know she was in a lesbian bar, so that is why she left. She offers to sleep with him if he doesn't tell anyone she was there - he thinks there is little evidence there to cover up and he takes her up on her offer. She tells him to pick her up the next day. Bucky doesn't tell Lee about this lead.

When he arrives at her house, she tells him that her dad found out he was a boxer and he wants to meet him. There is a very weird scene at the dinner table. Emmet Linscott brags about his money and connections and how he and his friend George made their way in Hollywood. Unfortunately George never got it together, but he's still helping out Georgie in his own way. Madeleine has a sister, who asks to draw Bucky, and Madeleine's mother is a society matron, hopped up on pills and with a real hate on for her husband. She makes a scene, the dinner ends but not before Martha hands over her drawing - an x-rated scene of madeleine and Bucky together. Despite all this, they check in to the Red Arrow Motel and they have sex. Afterwards, Madeleine tells Bucky that, yes, she actually did know more than she told him - that she wanted to meet the Dahlia since everyone said they looked alike, so she left messages etc and did meet the two girls. But they were boring and she lost interest quickly. Is that all? says Bucky, ,who doesn't like being unethical. And she insists that is it. Bucky is really drawn to Madeleine, although he knows it's not a good thing, but it keeps his mind off what is going on with Kay and Lee. He thinks he can handle this much and hopefully no one else will find this lead - it really goes no where

A few things happen in quick succession. They find Lorna, who is carrying with her a smut film starring her and the Dahlia. The department watches it and sees an obviously distressed Liz Short acting out a lesbian porn scene with the underage Lorna. Lee decides he's had enough and freaks out and leaves the room. Loew says to Bucky - he's off the case, see that he's here 8am tomorrow morning, or he's suspended from duty. The next morning Lee doesn't show up. Meanwhile, Junior Nash, the person they were tailing before they got on the dahlia case, was shot during a robbery, but not before he shot several other innocent people. Lee returns to the station house with bloody hands saying that he was as upset about the Nash thing as Bucky, but Bucky beats him up, angry that he allowed Nash to get away and violence occured. Lee takes off again. Bucky goes to his house to find him, but Kay is there. She tells him that he found out that Dewitt was in LA and got a tip where to find him. Bucky goes there to stop him before he gets into more trouble, or before Dewitt kills him. He runs into Dewitt and harasses him - Dewitt laughs and says that he has no beef with Blanchard and couldn't care less, the only thing that has Lee riled up is that they both slept with the same whore (language cleaned up here!!) Bucky is in love with Kay, so he freaks out to hear her being called a whore and starts beating up Dewitt. He hears gunshots (actually this whole scene is very different from the book, so I'm going on memory here) and he sees Blanchard who has shot dewitt, but at the same time someone comes up behind Lee and starts strangling him. There are two people, and Bucky only sees one of them, Lee is killed by the second person, and his body is later destroyed so that he will only come up as disappeared and no one will know what happened. There is a reason for this in the book, but this is a big plot hole which I won't get into right now. Bucky goes back to Kay, tells her that Lee is dead and there is much crying.

This is a part where the movie veers from the book. Basically, Bucky keeps sleeping with Madeleine until she fesses up that she actually slept with Liz Short - Bucky is disgusted at her for lying to him and can't trust her, so he walks out on her. He realizes he loves Kay and moves in with her (in the book this happens over a longer period of time, and the Madeleine affair ends well before he takes up with Kay - he refuses her for a long time, until something happens in the Dahlia investigation that he can't handle - corruption, dirty cops, etc - and he goes running to Kay and asks her to marry him). One day, Kay asks him to fix some tiles in the bathroom. He finds some money stashed under the floorboards and it's money from the bank job that Lee supposedly busted. Bucky confronts Kay, who knew about it but her and Lee had decided to not to tell Bucky because he couldn't handle it - Lee and Kay lived well beyond a cops wages, Lee had said it was fight money, but he actually owed Ben Siegal (aka Bugsy) a lot of cash and had to pay up - the bank heist was part of it, Dewitt was in on it and took the fall in exchange for part of the stash, Lee got the girl. there was one witness who could tie them together and it was a guy by the name of Baxter Finch - the same guy that Lee shot dead, when bucky thought he saved his life. Bucky goes out of his mind when he finds out that his best friend was crooked and the woman he loves was in on it. So, feeling like scum, he runs back to Madeleine.

The conclusion is coming up soon, and the movie sort of rushes through a few clues that allow Bucky to solve the case of the Black Dahlia. While in the Linscott's home, he notices that one of the men in a photograph looks like the guy who killed Lee. It is Emmett's old friend Georgie. There is a weird clown picture, an evil grinning clown I can't remember the explanation in the movie, but in the book it's the main character in a Hugo novel called 'the man who laughed' about a bunch of deformed children. The character has a smile that goes from ear to ear, just the same as the Dahlia was cut. Bucky remembers watching the movie 'the man who laughed' with Kay and Lee and the set was the same as the set in the stag movie that the Dahlia filmed. he confirms that he movie was financed by Emmett LInscott who had bought all this rotten timber and sets from the director and built a development that was destroyed in an earthquake and many people died due to shoddy materials used. Bucky goes to this deserted development, discovers the set and in the back he finds a bloody mattress. THere is black hair, and a running stream out back that was used to drain the body. Bucky knows he cannot go back to the police because Madeleine is somehow involved and he withheld evidence. He goes to her house where he discovers her in a weird embrace with her father. They confess that although they did not kill her, they did set her up. Georgie saw them filming the porn film and he fell in love with Elizabeth Short and wanted her, probably because she looked like Madeleine. Liz called the house one day, looking for money as usual. Emmett asked her if she would go on a date for money and she agreed, so they set her up with Georgie. They knew Georgie wasn't quite right - he like to slice up animals and his father was an anatomist, so he had a fascination with dead things, but they didn't think he'd kill her. When they saw the papers, they knew what he'd done and they worked on alibis, etc. At this point, Ramona, the mother, comes in to tell the rest of the story - she hated Emmett and had had an affair with Georgie - and Madeleine was his daughter. She hated georgie's obsession with this girl, she still loved Georgie and the only way she could get his attention was to share his dark secret, so she knocked out the girl and the two of them tortured her to death (this is more from the book, it's not clear in the movie, although she confesses doing the killing, then shooting herself).

The case is still unsolved as the Linscotts will do everything to keep their name out of it and with the killers dead, there will be no more clues. Bucky realizes that Lee had also figured out who killed the Dahlia and, needing money, went to the Linscotts and attempted to blackmail them, so that he could pay off Ben Seigal. He didn't go to kill DeWitt but to pass off the money and was killed by Georgie (who died in the attempt) and a mysterious other person who turned out to be Madeleine. He confronts Madeleine, realizes that she is truly evil and kills her. He then returns to Kay and lives happily ever after. The Dahlia case remains unsolved

As an aside, the book's conclusion is a lot less comical than the movie and much more satisfying. Bucky travels to Boston to find out some things about the dahlia's past and finds out that she's much more than the slut she appeared to be, he is able to reconnect with the Dahlia and extricate himself from Madeleine who is alive, but is far more manipulative than the Dahlia was. They looked alike and at times Bucky is unable to tell them apart. In the end though he comes to terms with the persons they were. This parallels with the author's own demons and obsessions with the murder of his own mother and his feelings towards her. Many of Ellroy's characters struggle with moral dilemmas in an immoral world.