One of the things actress Laura Linney does so well is use her all-American looks – red-headed, clear-skinned, pretty but not quite beautiful – and play them off against complex emotions.

She did this triumphantly in “You Can Count on Me,” and worked variations in “Mystic River” and “The Truman Show.” Stay tuned for another turn in the upcoming “Kinsey,” too.

Linney’s different sides are highlighted to similar effect in “P.S.,” a low-budget character study in which she never leaves the screen. The movie’s scattered, but Linney doesn’t lose focus.

She plays Louise, late 30s, divorced, on the admissions staff at Columbia University. She is startled to find an application from a grad student who shares, exactly, the same name as a long-lost love of her youth.

This is F. Scott Feinstadt (Topher Grace), a painter. Her old boyfriend, who died 20 years ago, was a painter too.

When Scott shows up for his interview, Louise is provocatively dressed in a low-cut outfit. Clearly, she already feels something about this coincidence, and is too intrigued to hold back.

Thereby hangs a tale of passion and confusion. Louise is drawn to Scott not because of who he is, but because of her memories of her dead lover. Like Nicole Kidman in “Birth,” she’s projecting feelings onto a much younger person.

Based on a novel by Helen Schulman, “P.S.” does nicely whenever it sticks to these two people. It has a hot-funny sex scene that bares no skin but feels all too realistic.

Topher Grace, from “That ’70s Show,” is quick and bright, not at all a blank slate. Scott doesn’t know about Louise’s past, so he’s just perfectly happy this foxy older babe has taken an interest in him. (His reaction to their first sexual encounter, unprintable here, is hilarious and authentic.)

A sidebar plot about Louise’s rivalry with an old friend (Marcia Gay Harden) feels like something out of a Chick Lit novel, not quite fitting the central situation. The friend betrayed Louise’s friendship many years before, and she looks to do the same thing now.

Dylan Kidd, who made his directing debut with the entertaining “Roger Dodger,” does well at keeping a humorous approach to much of this, despite how serious it sounds. For instance, when Louise’s ex-husband (Gabriel Byrne, in shaggy academic mode) confesses his countless past infidelities to her, the scene is weirdly funny.

When it was over, I couldn’t help thinking the movie had lost its way from its strong early scenes. Linney gives it her all, but it isn’t quite enough to convince.

“P.S.” HH

Downhill: A woman (Laura Linney) in her late 30s becomes convinced that a young painter (Topher Grace) is somehow the reincarnation of a lover from her youth. Some sharp and funny scenes early on, but the movie seems to lose its way.

Rated: R rating is for subject matter, language.

Now showing: Crest

“P.S.” HH

Downhill: A woman (Laura Linney) in her late 30s becomes convinced that a young painter (Topher Grace) is somehow the reincarnation of a lover from her youth. Some sharp and funny scenes early on, but the movie seems to lose its way.

Rated: R rating is for subject matter, language.

Now showing: Crest