James Wan's Insidious opens with a sequence so patently ridiculous, so preposterously over-the-top, that it feels like parody--like something out of an early DePalma picture. It closes with a cheap, dopey, no-good ending that will absolutely infuriate any viewer with a triple-digit IQ. In between those two low points, the film crests and dips, veering wildly from irritating sidebars to genuine, honest-to-goodness scares. It's an almost comically uneven picture. But when it sticks to the business of being creepy, it does so with a ruthless efficiency; at its best, it's a mean, nasty little thrill-delivery system.

And it is, thankfully and at long last, a haunted house movie that answers the question Eddie Murphy asked nearly a quarter of a century ago: "Why don't white people just leave the house when there's a ghost?" In Insidious, after Renai (Rose Byrne) decides--in light of her son's bad fall that led to a coma and other strange events--that their new house is haunted, her husband Josh (Patrick Wilson) just moves them out. Joke's on him, though: the house isn't haunted. Their son is.

Saw director Wan (working from a script by Leigh Whannell) pulls out every trick in the book to make that house creepy: the sonorous ticking of a grandfather clock, the reverberating drip of a faucet, a clacking metronome, whispers on a baby monitor that turn into growls, and then into shrieks. Every door in this joint creaks--have these people never heard of WD-40? The devices are worn-out, but Wan can put a scary scene together; the sequence with a late-night intruder is indisputably gripping, its big scare landing with the blunt force of a hammer to the head.

After an appearance by a pair of tech guys, who engage in some ill-advised comedy team banter, Lin Shaye appears in what amounts to the Zelda Rubinstein role. Shaye is primarily known as a comic actress (she's a favorite of the Farrelly Brothers), but she's playing it straight here, and doing it well--this is a genuinely interesting performance, even when she's stuck mouthing inane metaphysical mumbo-jumbo about "astral projectors" and "travellers" and "the further," or when she gets with that old warhorse, "There's something we could try... It's a bit unorthodox."

That unorthodox move is a souped-up séance, and here Wan really pulls out all the stops--strobe lights, scary music, physical force, wagging tongues, you name it, they throw it in, right up in the camera and at top volume. The whole thing is done with a pounding abrasiveness, but I'll give them this much: the scene plays. It's got a kick to it; it's also the picture's last gasp of cogency. Josh's subsequent journey into "the further" (or whatever the hell it is) isn't nearly as successful; they end up dealing in abstract, fantasy jolts, set in some kind of Ken Russell wet dream, rather than the more austere and effective stuff that's grounded in a recognizable reality. It renders the climax a bit of a mess, but that sequence is a model for storytelling clarity when propped up next to the "have your cake and eat it too" resolution. You can't believe how badly it ends. People were laughing out loud at my screening.

But before it goes off the rails, Insidious has its moments. Wilson and Byrne, both good actors, don't get much in the way of character beats, but they make the most of what they get, and Barbara Hershey is properly haunted. I'm less than crazy about the look of the film (it's got a washed-out, barely saturated, highly antiseptic look), but Wan guides the actors well, and his smooth, gliding camerawork lulls us into complacency, which he's more than happy to thump us out of. Insidious isn't a good movie, not really. But it's brutal and piercing and more than a little crass, and it'll score some cheap thrills on a Friday night.

Jason lives in New York. He holds an MA in Cultural Reporting and Criticism from NYU.