David F. Sandberg’s debut feature—an expansion of a 2013 short—is essentially a one-trick pony, using a single horror trope over and over again. But although “Lights Out” is repetitive, it exhibits considerable ingenuity in varying the sole trick so that it doesn’t grow dull over the course of the movie’s trim eighty-minute running-time. While an effort to explain what’s been going on in the final act inevitably comes up short, the picture, while not as strikingly imaginative as “The Babadook,” shares with Jennifer Kent’s film solid craftsmanship and compactness, as well as some basic themes, that place it head and shoulders above most contemporary genre fare. Unfortunately, it’s virtually impossible to discuss the movie in any detail without spoilers, so those who wish to avoid them should probably stop reading here until they’ve seen it themselves.

The picture opens with a prologue in which Paul (Billy Burke) is killed by a creepy female figure (Lotta Losten) in a warehouse. The kicker is that the figure that leaves him a bloody corpse is perceptible–and able to do harm–only in darkness; light makes it disappear, like flicking a switch on and off.

That visual device is used throughout the film, generating periodic jolts as it occurs in clever variations. Paul, it turns out, was the second husband of Sophie (Maria Bello), a woman whose already fragile psyche is left devastated by his death. Her deterioration, which takes the form of conversation with a dark figure in her room, terrifies her young son Martin (Gabriel Bateman) to such a degree that the poor kid can’t get any rest and falls asleep in class. When the social worker overseeing the family’s case can’t get in touch with Sophie, she calls Martin’s stepsister Rebecca (Teresa Palmer), who moved out of the house some time before. She retrieves the boy and takes him home, but, after finding Sophie in a terrible state, takes him to her place. CPS intervenes, however, and forces her to return the boy to their mother.

Martin, however, immediately finds the spooky happenings in the house intolerable, and flees to Rebecca again. That ultimately leads the girl and her slightly goofy but charming boyfriend Bret (Alexander DiPersia) to take the boy home, but also to agree to stay in the family homestead to calm his fears. Instead, of course, they find themselves in as much peril as he is.

The reason behind the danger is, of course, that shadowy murderous female figure, which turns out—as Rebecca discovers from research material collected by Paul—to be connected to an ill, emotionally disturbed girl named Diana whom Sophie had become close friends with during a childhood stay in a mental institution. The girl died in experimental treatment, but her spirit seems to live on—though whether as an actual ghost or as a projection of Sophie’s disturbed mental state is an open question. Rebecca, Martin and Bret will need to be smart and quick to stay alive, especially when—as one must expect—there’s a power outage. As “The Conjuring 2” made clear, not even the cops can offer much help. Motherly love, however, is another matter.

“Lights Out” combines elements that are the meat and potatoes of contemporary horror movies—not just a creepy menace and an oddball hook, but also a spunky heroine, a cute kid in peril, and a mildly obtuse but supportive male to provide some support, however ineffectual. But if the ingredients are far from extraordinary, they’re mixed with skill and even a bit of elegance. Eric Heisserer’s script can’t tie everything together logically, despite an effort to do so via some spectral messages painted on a basement wall toward the close, but Sandberg skates over the plot holes briskly (aided by the fleet editing of Kirk Morri and Michel Aller) and delivers the shock moments without resorting to a ton of blood and gore. He also elicits strong performances from all four leads, who earn sympathy even if their characters are sketchily written. Bello exhibits an appropriately haggard air and Palmer suitable resolve, while Bateman avoids the obnoxiously precocity of so many kid actors and DiPersia proves irresistibly likable, earning gasps that turn to laughs in a last-act chase scene that proves how adeptly the film combines the two. The visual effects by the Aaron Sims Company are genuinely unsettling, and the technical work—by cinematographer Marc Spicer, production designer Jennifer Spence, and sound editor Bill R. Dean—is topnotch, while Benjamin Wallfisch’s background score ratchets up the tension as required. The canny combination of light, shadow, and sound so integral to the picture’s success is a testament to their teamwork.

Just as “Psycho” had some audience members avoiding showers more than half a century ago and “A Nightmare on Elm Street” kept them away in the eighties, “Lights Out” might leave them leery of dark places in their homes. But though it might lead to an increase in viewers’ electricity bills and expenditures on candles and flashlight batteries, the scary fun will be worth it.