Natalie Dormer escapes the sexpot ghetto the movies (“Rush”) and TV (“The Tudors”, “Game of Thrones”) tried to sentence her to with “The Forest,” a ghost story about twins — one lost, perhaps suicidal, the other hunting for her sibling.

“Forest” is what we call “a January horror movie,” promising only a couple of hair-raising moments. But Dormer acquits herself tolerably, and the Japanese setting doesn’t hurt.

That’s where Aokigahara Forest sits, at the base of Mount Fuji.  And that’s this movie’s $12 million (its opening weekend take) idea. There is a real forest so popular as a suicide destination that it world famous for it, and there is a semi-formal infrastructure to deal with it.

Three screenwriters and first-time feature director Jason Zada (he scripted “The Houses October Built”) play around with that when Sarah (Dormer) arrives there.They find jokes in the locals’ matter-of-fact treatment of suicide. A country whose population is shrinking and aging and remains determined to take the whales down the tubes with them? The resignation about suicide fits.

Sarah’s twin sister, an English teacher living in Japan, went missing in the forest. Everybody fears the worst. But Sarah has twinsense.

“She’s not dead,” she says. She’s sure of it.

But the forest is both a bucolic and a haunted place. It has rules. And even though Sarah has a guide (Yukiyoshi Ozawa) and a hunky travel writer (Taylor Kinney) with her on her search, she should follow those rules.

“Never leave the path.” Don’t go in “with sadness in your heart.” The forest messes with that sadness. Sarah breaks the rules.

Simple camera angles, a little makeup and hair dye and slightly altered accents make Dormer convincing as American twins. She plays the rising paranoia and moments of terror adequately, if not quite compellingly.

The best scenes are when Sarah is invited downstairs where a receptionist at the park office is sure they have her sister.

“What is this place?”

Dramatic pause.

“The basement.”

The body? It’s not Jess, the sister. Not to worry. There’s always tomorrow, the helpful Japanese lady says.

“Come back. More bodies.”

There isn’t much more to this than that — a couple of frights, a growing suspicion, and some dry jokes. Kudos to Dormer for getting a paid vacation to Japan, and not having to strip to play it.

MPAA Rating:PG-13 for disturbing thematic content and images

Cast: Natalie Dormer, Taylor Kinney, Yukiyoshi Ozawa

Credits: Directed by Jason Zada, script by Nick Antosca , Sarah Cornwell and Ben Ketai. A Gramercy release.

Running time: 1:33