One of the main unifying traits that connects nearly all the filmmakers who were part of the New Hollywood Cinema period (not every last one, of course) was their knowledge of cinema. For most of them, this was the result of having gone through film school rather than come up as an apprentice, the way most film artists prior to the early 1970s had done; they were the first generation trained in cinema history and to have absorbed the theories of the French critics in the '50s and '60s as an academic truth. They were, in short, the first American filmmaking generation as to be on the whole cinephiles, in the sense that we now use that word.

This meant different things in different individual cases, but I bring it up now because we're about to set our sights on Brian De Palma, who presents one of the clearest examples of "film buff as film director" in the history of the medium. I suspect that the one thing people know about De Palma if they've heard of him at all, is that he's the director who made all of the Hitchcock pastiches. This is unfairly reductive - you can count on one hand the number of De Palma films that are primarily Hitchcockian - but the lines of influence are clear and unmistakable.

So with that, let us turn to 1973's Sisters, De Palma's seventh feature in five years, and also one of those primarily Hitchcockian films. In fact, so consciously was the director looking towards the great Hitch for his cues that he used an assortment cuts from Bernard Herrmann's scores for Hitchcock movies as his temp track, before talking the actual Herrmann out of retirement to write the "original" score. And those scare quotes aren't optional - there are moments, right from the very beginning, where the music isn't riffing on Psycho and Vertigo, so much as directly lifting from Psycho and Vertigo with a couple of notes switched here or there to make it at least slightly unclear what's up (sometimes, it dives into electronic music that sounds nothing remotely like any of Herrmann's work with Hitchcock) But it works in its new context, and really that's the only thing we need to be particularly worried about.

As for De Palma's story, which he turned into a screenplay with Louisa Rose, it's superficially quite a blast of Hitchcock in its own right: the first act plays the same "false protagonist who suddenly dies" card as Psycho, and the second act steals "sometimes apartment dwellers can see terrible crimes being committed across the way" straight from Rear Window. That film also supplies a number of individual story beats, and many of the individual shots and story ingredients crib from some Hitchcock film or another, right up until a final scene that works as both homage to and parody of the final shot of Psycho, the one with the car housing a corpse being dredged up from the swamp.

The important thing to note in all of this is that Sisters isn't simply an exercise in remixing classic thrillers for the sake of showing off De Palma's knowledge of film history. Which I confess had been my impression for many years, and was the major reason I've put off watching till now. It's craftier than that; it starts at Hitchcock and then pushes forward, making a fantasia on Hitchcockian themes with the angry energy of the new. For all its nods towards classicism, Sisters is a vigorously '70s movie, in its psychosexual raggedness (long before "psychosexual" had become the most clichéd way of describing any kind of thriller), and the ugly frankness with which it depicts the streets and buildings of New York. And its primary mode of tension and horror is forward-looking as much as it's conservative - there are moments whose staging and conception anticipate David Cronenberg more than the look backwards to Hitchcock or anyone else.

And all of that misses a pervasive truth of Sisters that I expected not at all, and was delighted to find: it's a funny movie. Perversely, darkly funny, sure - the opening credits are photographs of human fetuses, delicately positioned to stare at the camera with dark scowls of murderous rage, and it's as discomfiting as it is hilarious. But there's also room for the grand absurdity of the fake game show where we enter the story, Peeping Toms, something like a sexualised Candid Camera, in which hidden camera capture victims in awkward situations, with a panel of players asked to guess how they reacted to their situation. Our particular game concerns Phillip (Lisle Wilson), who's stunned to see a gorgeous blind woman, Danielle (Margot Kidder, who dances nimbly at the edge of comedy with a big ol' Québécoise accent) wander into the men's locker room and start changing. He has the good grace to leave quietly without watching or humiliating the woman - who is, of course, an actress, and can see just fine - and so wins two dinners at a fancy restaurant. After the show she suggests that he takes her out on a date with his prize, during which meal they're interrupted by her intense and frightening ex-husband, Emil Breton (William Finley). It's not enough to dissuade her from inviting Phillip back to her place on Staten Island, where they have sex after tricking Emil into thinking they were parting for the night.

The next morning, Phillip overhears an argument between Danielle and her identical twin sister, Dominique - by this point, we've already seen the enormous scar on Danielle's right hip, as accompanied by an electronic sting on the musical score that is much too freaked out the scar and much too anxious to make sure we absolutely pay all of our attention to it, so we've got quite a head start on figuring out exactly what kind of twins they are - after which Danielle emerges and asks if he'd be so kind as to pick up her pills, while also idly mentioning that it's her and her sister's birthday. On the way home from the pharmacy, he decides to use this information to play a nice surprise, buying the twins a cake, and this proves decisive; the delay in taking her medication sends Danielle into a writhing fit on the floor. By the time Phillip gets back, Danielle is nowhere to be seen, and Dominique is asleep on the bed; when Phillip rouses her, she grabs the knife he brought to cut the cake, cutting him in each of his femoral arteries (or, cutting him twice in the same femoral artery; there's bad continuity racing throughout the film, and some of it is clearly intentional, but this is one of the places where I think it probably isn't), letting him bleed out.

This is witnessed from across the alley by Grace Collier (Jennifer Salt), a columnist with a local paper who has managed to get herself in trouble with the local police thanks to an article titled "Why We Call Them Pigs", among other attempts to rouse the populace in radical anger, from her tiny little soapbox. "Yes, the Grace Collier, I wrote that story" she sighs on the phone with the cops, in a beautifully petulant comic line delivery that I wish I could bottle and listen to every time my spirits were low. She eventually convinces them to come over to check things out, at which point things start to get interesting as all hell: to sell her story, she starts piling on details that we know to be true, because we were in the room when Phillip died. But Grace wasn't, and she could only see a fraction of the killing from her apartment - this we know because we see the image as she sees it, and it's even put into a zoom backwards to make sure we notice just how circumscribed the angle she has into the room is.

The police find nothing, so Grace persuades her paper to let her do some investigative reporting, which they'll only do after assigning her a private detective, Larch (Charles Durning), to help. What they find is at times not remotely surprising (Danielle and Dominque were conjoined twins, a fact the movie tries so little to hide that it shows up in the ad campaign), and is some places enormously surprising, and at some places is surprising primarily because the movie made one twist that doesn't happen seem incredibly obvious, so we were looking the other direction while a different twist altogether sneaks up on us. It would be shabby to give away more - this isn't a Psycho, where it has become such a carved-in-granite classic that everybody knows how it ends. Let us leave it with: the things you expect to be revealed are all cleared off the deck early enough that the film has enough time left over to go into places that I did not see coming at all, tranforming flawlessly from a horror-tinged mystery about shady Québécois doctors going to extraordinary lengths to hide their professional and personal sins from the world, into a surrealist nightmare about having one's identity pulled out from below, and one that revises the question of who these people are so definitively that the ellipses and confusing loose ends the film was teasing us with earlier turn out to be nothing but its most dramatic sleight-of-hand.

It's an extremely unsatisfying conclusion, but it's hard to imagine one that would fit better; even the fact that it's unsatisfying plays off the film's depiction of the limits of what we perceive and how we interpret it; sometimes you just don't fucking know what's going on, and Sisters is, among other things, a big tease in stretching out our pleasant misery at not being able to solve all of its mysteries. Really, it's mostly a game in perceptual exercises overall, from its deliberate employment of continuity errors to its fun use of split-screens: at one point the film shows Danielle and Emil's desperate attempt to clean-up after Dominique (another Psycho nod) in one half while Grace's frustrated attempt to get the cops to god-damn go upstairs already plays in the other, a nifty way of building tension through style that mere cross-cutting wouldn't be able to achieve, while also making demands of our attention that we're of course not quite able to meet, and so the film once again points out that stuff is going to happen and we can't figure it all out.

There's an attempt at social commentary here: the brutishness of cops towards women and minorities is an obvious point the movie wants to touch on, though it does so only glancingly. It's more sustained in looking with horror at the abuses of power by authoritative men, with its final twenty minutes a sustained flurry of sucker punches that manage to show how such abuses can continue on in the world even after the abuser is dead. But the things that are most lingering about Sisters are generally stylistic: it's the flair with which De Palma stages his imagery that lingers more than what those images denote. A bright red spot on a sofa there, shallow focus to make it all the clearer how much the film is preventing us from seeing there, and plenty of skillful lifts from Hitchcock. It's a bit more surface level than it entirely wants to be, and the wackiness in the performances from Kidder (inadvertent) and Salt (deliberate, or at least successful) don't serve to give it any more depth, though they do make it quite a bit more fun. And when that fun suddenly flashes to sharply-honed cruelty, the film packs a hell of a lot of punch for something that's basically an insubstantial genre exercise. It's a terrifically smart piece of craftsmanship that keeps slithering out of your grasp; maybe not a great cinema by the usual standards, but I found it a compulsively addictive viewing experience.

Body Count: 2, and its surprisingly unambiguous about that number, considering how much else it's ambiguous about.