Because it wasn’t entirely clear to me when I left the theater just who had done what to whom, and why, you needn’t worry that I will give away the plot of The Black Dahlia. All I really understand about this story of late-1940s Los Angeles–not so much a city, you’d think, as a tar pit, bubbling with near-universal ickiness–is that a character in it once slapped up a shoddy housing development, using materials scavenged from Mack Sennett’s studio.

As with the setting, so with the film itself: The Black Dahlia turns out to be something of questionable structural integrity, pieced together from old movies.

Normal filmgoers may now stop reading, knowing that The Black Dahlia will not give them the usual satisfactions of a good story told on Saturday night. Only viewers with the patience of true auteurists are likely to be rewarded by The Black Dahlia. They will have seen Brian De Palma before at his directorial games and will expect him to treat this plot as a distraction, in two senses of the word: as an inconvenience to be endured and as a diversion to hold the viewer while a trick is done. The question is, what trick did De Palma carry off this time, under the pretext of making a police thriller? What might it mean that the form of his new movie flagrantly imitates a crime?

The beginnings of an answer lie in the movie’s source material–a well-regarded novel by James Ellroy–and in the real event that provided the core for Ellroy’s fiction.

In early 1947 the naked corpse of a 22-year-old woman, Elizabeth Short, was discovered in a vacant lot in downtown Los Angeles. In life, as one of Hollywood’s innumerable aspiring actresses, Short had stood out only because of the black wardrobe she’d affected, set off by a flower in her long, wavy hair. In death, she was distinguished by the gruesomeness of her murder. Even Jack the Ripper’s victims had not been so mutilated. In the public’s mind, or the part of it that was fed by newspapers, Elizabeth Short’s hacked-up body quickly became a site where fantasies coalesced: images from the movies and about the movie business, fears about city life, anxieties about the sexual wants of young women. A fascinated city took to calling Short the Black Dahlia–substituting a lurid nickname for an obscure, now-unknowable person–while telling itself endless stories of what she might have done, and how she might have died.

Too many stories? According to the fictional narrative of The Black Dahlia, people who ought to have been thinking of other things were busy instead with the Elizabeth Short mystery, and so allowed all manner of betrayals, tragedies and crimes to play out. (Auteurists may insert here a list of earlier De Palma films that dwelt on the sin of prurient inattention–I’ll spot you Body Double–and for ten bonus points may cite precedents from the work of Alfred Hitchcock.) But, to stick to the case: Among the distractable types in The Black Dahlia, none is more at fault than the film’s point-of-view character and voiceover narrator, a young police detective named Bucky Bleichert (Josh Hartnett).

He’s unreliable, of course–and not just because he’s set up as the standard film noir sap, infinitely gullible and infinitely horny. The very first shot in the movie finds Bucky in the locker room of a boxing arena, preparing to fight in a publicity fundraiser for the police department. The story you’re about to hear is therefore being recalled by a guy who’s had his brains rattled. Punch-drunkenness may help explain, if not excuse, the ensuing fuzziness about who did what, etc. It certainly provides the only possible justification for later episodes in The Black Dahlia that are so clichéd as to seem lifted from a 1947 B picture, or so preposterous as to be worthy of a Monty Python broadcast.

We are not just watching a movie about the workings of the public imagination; we are temporarily shut within those imaginings. So, when people make love, they must tear at one another’s clothes, rip the cloth and dishes from the dinner table (since no other horizontal surface is immediately available) and never, ever close the venetian blind. (Auteurists take note: Hartnett keeps his hat on, paying tribute to Michel Piccoli in Contempt paying tribute to Dean Martin in Some Came Running.) Expository dialogue must be rattled off as quickly as possible, sometimes in a state of hysteria, just to satisfy the audience that an explanation has been given (even if it can’t be followed). Revelations about someone’s character, by contrast, must be shouted at the viewer and then repeated so they sink in–as when the story’s enigmatic blonde (Scarlett Johansson) catches Bucky with the plot’s enigmatic brunette (Hilary Swank) and bellows, “She looks like that dead girl!! How sick are you?!” Because Johansson’s character is one of the common people, she is afforded this melodramatic gravitas. Swank’s character, though, is a rich girl whose father and mother talk in phoney-baloney accents, and so they are treated as comic grotesques.

Does The Black Dahlia ever touch on a credible human reality? Yes–though it does so, paradoxically, during a few glimpses of the absent mystery woman. You see Elizabeth (Mia Kirshner) only as an image in various black-and-white films–screen tests, for the most part–that Bucky has located for his investigation. These are scenes of routine, unquestioning male domination. A man’s voice, offscreen, insistently mocks and berates and insults Elizabeth, while she gives the camera all she’s got: a flirtatious smile that won’t hold, and a few transparently false stories that she hopes will make her impressive. In each of these little movies, the artifice breaks down. Elizabeth will keep telling a lie, knowing it’s not believed, until she sinks down next to a radiator, where she begins picking at a run in her stocking. She is now talking mostly to herself, as a child does, while the man’s voice, making fun of her and asserting an employer’s prerogatives, reminds her that she’s a full-grown sexual commodity.

If you think of pornography in terms of power relationships, then this is a stag reel. It is a stripping down–even a kind of murder. And this is the one place where a character in The Black Dahlia steps out from the quotation marks and truly comes alive. You may understand, then, why De Palma feels he can trifle with the plot mechanics of fictitious crimes, having re-enacted a real crime right before your eyes.

That’s the trick in The Black Dahlia–a good enough trick to make up for at least some of the longueurs, improbabilities and self-indulgent gags that trouble the movie’s surface. There is, for example, a laboriously established but weirdly unrealized love triangle among Johansson, Hartnett and another police detective, a flashy wiseguy played by Aaron Eckhart. If the plot of The Black Dahlia were to be taken seriously, then the home of this threesome would be the film’s emotional center. Instead, it’s a place where De Palma drops in to visit from time to time. Eckhart, who is a slick actor when he wants to be, is directed to preen, scowl and rage like a bus-and-truck company’s Snidely Whiplash, while Hartnett mostly gets to peer at the world through slits so narrow that he seems not to have eyes at all. Granted, Hartnett’s character suffers from moral and practical blindness; but it’s too much, the way his face (too prettily smooth to be a boxer’s) is reduced to a contrast of pillowy lips versus hirsute brow, with nothing holding them apart except for a squint. Bucky’s style in the ring is supposedly cold and analytical, but nothing in either the script or the performance hints at such shrewdness.

Hilary Swank would probably take him in one round, but she’s stuck being the femme fatale. Scarlett Johansson wears a cloche hat and uses a cigarette holder.

So all right, De Palma’s trick maybe doesn’t make up for all of the longueurs, improbabilities, etc. Still, his moviemaking instincts are so strong, his habits of thought so incisive, that The Black Dahlia at its best is breathtaking.

Here’s how he distracts you early in the picture: Hartnett and Eckhart are sitting in a car, staking out the cheap hotel where a thug supposedly holes up. As they wait, a crane shot takes you up the facade of the flophouse and over the roof, so that you see a panorama of the back street and the open land beyond it. There, far below you, a woman is walking by. Suddenly, she begins running along the street, screaming for help. A car is turning the corner, and the driver must certainly hear her, but he just picks up speed, ignoring her attempts to catch up. Though the camera is already in motion, you’d think it would pause on the desperate woman, or even change course and descend to her; but instead, as if acknowledging the heartlessness of the world, it just continues on its course, following the car back out to the main street, where the cops are continuing their stakeout. The pleas will not be answered; the running woman will get no help.

So the corpse of Elizabeth Short, newly discovered, is left in the tall grass behind the hotel. They were never wrong about suffering, the old masters.

* * *

I think you will recognize the characters in Kelly Reichardt’s Old Joy. The slim, glum, eagle-nosed one pieces a living together in Portland, Oregon, listens to Air America and now, on the verge of middle age, is about to become a father. He is so self-involved that when he abruptly takes off for the weekend, leaving his wife to fend for herself at about nine and a half months, he thinks she’s the one who should be more considerate: “I’m not going to enjoy myself if you’re miserable about it.” The buddy with whom he’s traveling–thickly bearded, ginger-haired, balding–seems to have no purpose in life beyond getting his mind blown: at meditation retreats, at Big Sur bonfires, at adult-ed courses on topics he doesn’t study (but is sure he understands). His shirt is misbuttoned over a pot belly; he shows signs of living in his van.

These are Mark (Daniel London) and Kurt (Will Oldham), whose brief camping trip up to the Cascades provides the sole action of Old Joy. Nothing could be simpler; nothing, apart from an early Warhol film, could be less eventful. And yet the immaculately photographed landscape works on you, as it opens up from industrial Portland to the mountains; the closely observed exchanges, which are so rambling and yet leave so much unstated, make the silences between Mark and Kurt echo with regret, longing, hope.

Old Joy is based on a short story by Jonathan Raymond, who wrote the adaptation with Reichardt. Peter Sillen gets credit for the beautifully evocative cinematography. In New York, the picture is playing at Film Forum through October 3.