Adapted from the book by Susanna Moore, Campion’s vision of a woman coping with fear and newfound sexuality is unique and powerful, yet ultimately undermined by the conventional conceits of the thriller. Despite the film’s bringing to life one of the nastier portraits of downtown Manhattan in ages, it’s hard to imagine that the movie’s gore-laden crime scenes will please either fans of Campion’s prior tale of sexual repression, “The Piano,” or the well-documented hordes who can’t get enough of Ryan’s trademark cuteness.

But their response won’t come close to the visceral revulsion that fans of mainstream thrillers will feel as they’re subjected to Campion’s endless array of pretentious, artsy touches and to so many plot holes that the movie could be sold as imported Swiss cheese. The only moviegoers who won’t be disappointed by “In the Cut” are those wishing nothing more than to catch Ryan in the buff.

Adapted by Campion and Moore, the movie provides Ryan’s Frannie with no shortage of men to fear or dark feelings to repress. Especially after a woman’s decapitated head turns up in her TriBeCa garden. Chief among the suspect males is Ruffalo’s smooth-talking Malloy. Charged with investigating the killings, Malloy also happens to sport a tattoo similar to one Frannie glimpsed on the man she believes is responsible for the grisly murders.

With each passing scene, “In the Cut” becomes more and more improbable, reaching a zenith when Frannie gets mugged late one night. Guess who conveniently materializes out of the shadows to take her home? Uh-huh. And then we’re supposed to swallow that it’s in this terrified state when repressed Frannie feels her libido and beds Malloy?

Malloy isn’t the only man lurking on Frannie’s periphery. At times it seems as if half the male population of Manhattan is stalking our mousy little professor, so they too become potential suspects. Included in this cadre of cads are John (an amusing Kevin Bacon), Frannie’s borderline psychotic ex-boyfriend; Cornelius (Sharrieff Pugh), a student who turns in a report written in blood defending serial killer John Wayne Gacy; and Malloy’s partner, Rodriguez (Nick Damici), a man with such a violent temper the department has taken away his service revolver.

Although Campion has been quite vocal in expressing her contempt for the conventions of the thriller genre, she has no earthly idea how to go about subverting or exploiting them for a more satisfying mainstream movie. Tossing in the occasional red herring or trying to create suspense are dramatic afterthoughts. Campion is much more interested in exploring the relationship between the erstwhile lovers, as well as that between Frannie and her emotionally fragile half-sister, Pauline (deftly portrayed by Jennifer Jason Leigh, who’s made a career out of playing similar characters).

Frannie moves in with her sister after the mugging — which requires another huge stretch of our imagination considering that Pauline lives above a sleazy bar! With all that sexuality and sweaty humanity pulsing and throbbing beneath her, Frannie’s compelled to share her unsettling dreams about her father’s unconventional courtship of her mother. Played out in equally unsettling black-and-white fantasy sequences, the images flicker on the brainstems of audience members, who squirm uncomfortably in their seats like unwilling voyeurs.

Then “In the Cut” really falls apart, growing more unbelievable with each scene, as Frannie blithely ignores a multitude of danger signs that even the densest, dumbest teen-slasher-bimbo couldn’t overlook. It’s painfully obvious that Campion’s intentions were to craft a film that could be viewed as both an art film and a commercial thriller. Sadly, she fails at both. ** S