Anchored by a quietly engrossing, wholly unaffected performance by the astonishing Samantha Morton ("Minority Report," "Sweet and Lowdown") as a young Scottish woman in shock over her boyfriend's suicide, "Morvern Callar" is a subdued film of abstract psychological detail.

The opening shot of Morton's pensive, pretty, everygirl face bathed in the blinking, buzzing glow of Christmas tree lights has a startling effect as it pulls back to reveal that she's lying on the floor of her apartment beside the body of her lover -- who left her only his ATM card and a note on his computer that begins "Sorry Morvern. Don't ask why. It just felt like the right thing to do."

Extraordinary in its initial simplicity, the film doesn't move outside this sparse, low-rent flat for most of the first reel, as the trauma-detached Morvern (Morton) runs her hands over the cold body trying to connect with her emotions as the truth of what has happened sinks into her soul. She opens her Christmas presents with silent introspection, examining the snaps on a new leather jacket the boyfriend bought her as if she knows that the minutiae of this moment will be burned in her memory forever.

It's not until much later that she reads the rest of the suicide note and discovers he's left her a disc containing the novel he'd finished just before slashing his wrists. The manuscript becomes a catalyst for her precarious emergence from this emotional abyss when she replaces his name on the cover page with her own and sends it out to publishers.

When "Morvern Callar" hones in on its core elements -- the girl's fractured psychological state, the body (which she leaves right where she found it for most of the movie) and the novel she's claiming as her own -- the film is at its most absorbing.

Morton's penetrating but minute expressions of deflected grief are the picture's potent touchstones of emotional veracity and can lead to understanding some of her strange choices because the actress effectively pulls you inside her head. (The experience is aided by the soundtrack, which exists only when Morvern listens to a mix tape made for her by the dead boyfriend.)

But when director Lynne Ramsey ("Ratcatcher") stands on the outside looking in -- essentially whenever Morvern leaves the apartment -- the focus seems lost and the bewildered randomness that drives Morvern's spiritual reparation begins to give the film a scattershot quality. Ramsay has a muted storytelling style that requires the audience to actively engage the character on a subjective level -- but it's a laborious process that isn't always worth the work.

As somber Morvern takes off to the Spanish coast with a carefree girlfriend (Kathleen McDermott) because she can no longer cope with the drab normalcy of her everyday life, her behavior becomes erratic. She sleeps with a spring-break partier, but it's not clear from the narrative if she's met him before or not. She drags her friend on a cab ride to a small village, then leaves her on a remote road in the middle of the night. And because these episodes don't naturally connect with the character on that subjective level the way the apartment scenes do, the film soon seems as lost as its heroine.

I can't help but wonder if the book from which the film was adapted (by Gen-X Scottish author Alan Warner) might not be a largely internalized affair that simply lost something when it was forced into a third-person perspective by the very nature of cinema.