In the Cut is being marketed as a thriller, which is curious because the only thrilling things about it are the intense, unwavering mood director Jane Campion is able to sustain, the against-type, impressive performance by reformed cutie-pie Meg Ryan — and the fact that despite extremely bad press coming out of the Toronto Film Festival, where the audience reportedly hissed at the ending, this is not really a terrible movie.

Nor is it a really good one. Ryan, under blunt brown bangs, plays the sullen, sexually needy Frannie, a writing professor who seems to have some sort of paralysis preventing her from smiling. Things don’t get much cheerier for Frannie when she falls in with gruff homicide detective Malloy (Mark Ruffalo) after a woman’s head turns up in her garden. Graphic sex, and not much else, ensues.

Campion, who co-wrote the script with Susanna Moore (the movie was adapted from her 1997 novel), has done a remarkable job of capturing gritty lower Manhattan, and the tentative, dreamy haze Frannie wanders around in, hanging out with her messed-up sister, Pauline (Jennifer Jason Leigh), and being stalked by a former lover (Kevin Bacon, who is not credited because, he claims, it’s such a small role he didn’t want to steal Ryan and Ruffalo’s thunder.)

The biggest problem with In the Cut is that fancies itself a serial-killer mystery, but there is really no mystery about who is doing the killing, save a few blatant red herrings. And yet, somehow, it more or less holds your interest.

Ryan, who here inhabits a very different New York than she did in When Harry Met Sally or You’ve Got Mail, has a lot to do with what works. It may be ridiculous to call an actress brave for taking her clothes off, but there does seem to be something fearless about Ryan’s performance here, and her brazen nudity is part — but not all — of it.

Ryan, who will be 42 next month, looks amazing. Whether that’s due to rumored recent plastic surgery or not going within a mile of a carbohydrate for several years, or a combination of both, is a mystery deeper than any contained in the movie.

But as good as she looks, it’s Ryan’s performance that really surprises. It’s hard not to look for cracks — the lugubrious, languid pace gives you plenty of time for such things — but there really aren’t any to be found. You expect playing someone so dark to wear on her, but she seems perfectly at ease, perfectly convincing. Campion, who has faltered in the decade since The Piano, does a fine job of coaxing Ryan, and making In the Cut often seem more compelling than it really is.

Phoebe Flowers can be reached at .

IN THE CUT ** 1/2 (out of 4 stars)

A woman has an affair with the cop investigating a murder in her neighborhood.

With Meg Ryan, Mark Ruffalo. Co-written and directed by Jane Campion.

Running time: 119 minutes.

Rated R: Explicit dialogue, content and nudity; graphic crime scenes.