Sleep Paralysis, a sort of paralyzing nightmare, is a real phenomenon that affects a very large portion of the population, a graphic at the beginning of “Mara” tells us.

And historically, people in various cultures over the ages have thought it was caused by demons. That was given a visual manifestation when Henry Fuseli painted “The Nightmare.”

So “Mara,” a new horror thriller in the vein of “The Ring,” is parked on firmer footing than most boogeyman horror tales. It’s got cool-enough effects and moderately gloomy Savannah locations. For a genre picture, it’s not awful, which in horror is saying something.

Olga Kurylenko of “A Quantum of Solace” stars as Kate Fuller, a police psychologist called to a crime scene to A) because “You need to understand the reality of what we’re dealing with,” and B) talk a frightened little girl (Mackenzie Imsand) into saying who she saw do it. The cops are sure Mommy  Helena (Rosie Fellner) is the one who twisted Daddy’s neck.

Helena is alternately catatonic and hysterical. Sophie has her own answer to “Who hurt Daddy?”

“Mara!”

The detective (Lance E. Nichols, good) may want to label Helena a “certifiable fruit loop.” But Dr. Fuller hears her out.

“There was something EVIL in the room! And then I heard this awful music. And then I saw her, as real as you’re sitting there. MARA. I KNOW how this sounds!”

Kate immerses herself in sleep paralysis — talking to experts, sitting in on a support group. And that’s when she starts hearing noises in her house, seeing things in her tub, wondering how that glass of red wine shattered.

Supernatural thrillers like this require an “explainer,” and than man is a suspect. “Dougie” is British, lives like a hermit, “off the grid” and takes over the support group AND the movie as horror veteran Craig Conway (“Doomsday,” Estranged”) goes full-tilt crazy on everybody.

“She’s a DEMON! Whatever you do, do NOT sleep! Mara is REAL!”

Dougie pulls his eyelid down to show a blood blotch on the hidden part of the eyeball.

“Once you’re marked, that’s it. It’s over.”

“Mara” stumbles along between loving closeups of Kurylenko sleeping, extreme closeups of her waking in a start, stalked by this hairy skinny/bendy wraith that crawls through sheets and shower curtains.

The puzzle of the plot is far more interesting than frightening. Dougie has been taking the “Beautiful Mind” approach to “finding the connection.” He’s the one who gives us the etymology of this “demon,” the one who brings up this painting, now at the Detroit Institute of Art.

Director Clive Tonge, who also came up with the story, was onto something. The picture has a clever hook.

The deaths are grisly and flashes of closed-circuit TV footage deliver flickers of fright.

But there’s a reason those “Ring” and “Grudge” and many similar pictures make the demon zip into and across the frame. It’s a lot scarier than having this thing walk/stagger via insectoid joints, even if that’s the whole idea behind a nightmare that paralyzes — we see what’s coming, and we’re powerless to flee.

But when you slow everything to sleepwalk pacing, you deflate the frights and strip away the urgency that we and the characters should feel, the sense that something terrible is coming, that time is running out.

MPAA Rating:R for disturbing violent images, and language

Cast: Olga Kurylenko, Lance E. Nichols, Craig Conway

Credits:Directed by Clive Tonge, script by Jonathan Frank. A Saban Films release.

Running time:1:39