A true-crime author stumbles onto something beyond his beat in Scott Derrickson’s “Sinister,” which follows Ethan Hawke’s Ellison Oswalt as he grows increasingly obsessed with a missing-girl case he hopes will lead to a best-selling book.

Occasionally stupid (stretching even fright-flick conventions) but scary nonetheless, the pic should please horror fans.

Oswalt’s wife (Juliet Rylance), just uprooted to a new town (so he can investigate the new story) and already getting bad vibes from neighbors, asks, “We didn’t move a few doors down from a crime scene again, did we?” He assures her they didn’t.

She asked the wrong question: Oswalt has bought the very house in which four members of a family were slain, with the fifth abducted. An ornery sheriff (Fred Thompson) stops by before the boxes are even unloaded to warn the author he’s not a fan of his books, and doesn’t cotton to a fame-hungry scribbler second-guessing his department’s work.

Local lawmen are soon the least of Oswalt’s worries. He finds a box of Super-8 films in the attic, each showing a family being murdered in a uniquely grisly way. Believing he’s stumbled across his own “In Cold Blood,” he stays up nights scrutinizing the films and looking for connections between killings whose locations and victims are still unknown.

Derrickson borrows the vibe of Joel Schumacher’s “8MM” as Hawke, swigging whiskey and giving the crease between his eyebrows a workout, struggles with the horrible things he’s seeing. But the film soon shifts into bump-in-the-night mode, with an unseen visitor leaving clues for Oswalt in his own house and taunting him with increasingly unsettling (and harder to explain) stunts.

Setting aside Oswalt’s infuriating unwillingness to turn on the lights when homicidal intruders infiltrate his home at midnight, the movie has him doing some pretty unjustifiably dumb things – like walking with a butcher knife thrust in front of him when he has every reason to think his sleepwalking young son might suddenly leap out at him.

We allow him some of this, thanks to the picture’s coy suggestions that Oswalt might be going a little nuts due to the nature of his investigation. But Derrickson and co-screenwriter C. Robert Cargill are eager to draw in more familiar supernatural elements – an occultologist (Vincent D’Onofrio) identifies a crime-scene marking as a pagan symbol “dating back to Babylonian times” – and the movie’s proceduralist pleasure takes a backseat to ghosts and a mysterious figure known as “Mr. Boogie.”

The scares are effective throughout, helped a good deal by Christopher Young’s glitchy electronic score. While the end clearly points toward a possible franchise, though, many of the ingredients that make “Sinister” compelling wouldn’t make sense a second time around. Some of them barely hold up for the first.