Your pants. Do you like having them scared off you? Then you and your pants will enjoy “Sinister,” a deeply frightening horror film that takes its obligation to alarm very seriously. If this isn’t the most disquieting movie I see in 2012, I don’t know if I’ll be able to handle whatever is.

Ellison Oswalt (Ethan Hawke) is an author of true-crime books whose biggest achievement, the New York Times bestseller “Kentucky Blood,” was a decade ago. Increasingly desperate for another hit, he has moved to a small Pennsylvania town where the disappearance of a young girl and the murder of her entire family were never solved. He intends to immerse himself in the case, write a book, and maybe bring about some justice. His reputation for being able to find things the police missed does not endear him to the local cops, as represented by an unwelcoming sheriff (Fred Dalton Thompson).

He’s not too popular with his own family, either. His wife, Tracy (Juliet Rylance), is tired of moving to places where awful things have happened and being treated like a ghoul for it. Their 12-year-old son, Trevor (Michael Hall D’Addario), sometimes has night terrors, and is at the age where he wants to know the grisly details of his dad’s work. And little Ashley (Clare Foley), a budding artist, just misses their old house.

Ellison does indeed find evidence that eluded the cops, but not through any effort on his part. In the attic there’s a box of old Super 8 home movies that would seem to have been planted there by someone with intimate knowledge of the murders. These films are marvelously creepy, and Ellison is marvelously creeped-out by them. He’s also intrigued by the subtle clues they appear to offer.

Would you be surprised if I told you that Ellison starts to see and hear strange things in his family’s new house? Or that the murders depicted on those old films have more to them than meets the eye? Probably not. But what separates this from the average story about things that go bump in the night is the sheer dark intensity of it. “Sinister” has little use for levity or half-measures. Directed by Scott Derrickson (“The Exorcism of Emily Rose”) from a screenplay he wrote with C. Robert Cargill, the movie conveys its ghastly, unsettling ideas without watering them down (and, I might add, without being needlessly graphic).

Just a couple qualms. It’s insinuated that Ellison is reluctant to take what he’s found to the police because of something that happened with a previous book — he arrived at the wrong conclusion and did some real-world damage, apparently — but the nature of the incident isn’t explained, nor does it justify withholding smoking-gun evidence like he’s got now. Going to the cops with an alternate theory is one thing. Showing them a box of snuff films you found in your attic is another.

“Sinister” also leans on the jump-scares more than it needs to (and more than it should). With so many genuinely unnerving ideas, images, and events at your disposal, why keep using the cheap stuff? This is the unholy offspring of “The Ring,” “8MM,” “Blow-Up,” and “Poltergeist.” No pants are safe.

B+ (1 hr., 50 min.; R, violent images, some profanity, general scariness.)