Don't be misled by the fact that a quick summary of "P.S." sounds like a hokey Lifetime TV episode of "The Twilight Zone." The story does revolve around a Columbia University art school admissions director drawn to a young applicant who may be the reincarnation of her dead high school sweetheart -- but the possibilities of that spiritual element are just a jumping-off point for the complex, earthbound emotional baggage stirred up by her desire for it to be true.

The brilliantly instinctive and unaffected Laura Linney ("Mystic River," "You Can Count On Me") lends palpable weight and depth to long-dormant insecurities and desires in her melancholy, weary, authentically 39-year-old character. She is reinvigorated by the tumultuous affair she initiates with the cheeky, nascently charming young painter (Topher Grace), who shares not only an uncanny resemblance and his name with her lost love, but also his talent and his word-for-word desire never to live a "just add water" life.

Grace -- a worthy rising star whose comedic timing on "That '70s Show" is clearly just the tip of his acting iceberg -- perfectly embodies his art student's mounting curiosity and nagging consternation. He doesn't know what the hell is going on with Linney, but he's instantly drawn to her. She has a sad yet radiant down-to-earth beauty, she could hold the key to his artistic edification, and she's trying to seduce him -- so at first he figures, why fight it? Soon he becomes emboldened by the fact that her confidence as a woman and an authority figure evaporates around him, leading to a chemistry of pungent awkwardness between Linney and Grace that fills the screen like a fog.

Director Dylan Kidd -- who in adapting Helen Schulman's novel takes a 180-degree turn from his provocative sex-farce debut "Roger Dodger" -- vividly but unobtrusively captures the intimate details of every unguarded moment and complex sentiment in "P.S." He never telegraphs what Linney is thinking or feeling, knowing that an actress who can emerge from a sex scene with a genuinely flushed bosom and cheeks will produce a performance that goes well beyond words.

Kidd also landed a brilliant supporting cast. Gabriel Byrne plays Linney's ex-husband and closest friend (a professor who seduced her when she was a student herself) whose confession of a long-held secret sends her reeling in a scene of remarkably raw anguish. Gutsy Marcia Gay Harden makes a surgical-strike appearance as Linney's selfish, aging tart of a busybody best girlfriend, an unhappy Hamptons housewife who has her own jealous stake in the outcome of this curious affair. Paul Rudd ("Anchorman," "Clueless") is her recovered-addict brother, in whom she still puts little trust or faith, and Lois Smith ("Minority Report," "Twister") is the mother to whose protective cocoon Linney returns like a child when confusion consumes her.

"P.S." walks a strange and daring line that may not click with everyone. Absurdity is frequently lurking in its corners, as when Linney visits her time capsule of a childhood bedroom, where apparently nothing has been touched in 20-plus years (band posters are still on the walls, 1980s clothes are still in the closet).

But the confidence with which Kidd skirts this absurdity -- and even flirts with it at times through overripe romantic dialogue -- makes the film that much more thought-provoking for the way it plays into the beliefs that Linney constructs around her young lover. At its core, "P.S." isn't really romantic at all -- although it sometimes seems that way through Linney's eyes.

Apparently it seemed that way to composer Craig Wedren too, since the film's one significant distraction is the feel-goody, empowerment-anthem score, which is just too "Mary Tyler Moore Show"-pedestrian for a film this idiosyncratic. But "P.S." thrives on uncomfortable incongruity, so in a way even this could be seen as part of the picture's peculiar synchronicity.