Stephanie Daley, the titular young girl of Hilary Brougher’s intensely observed character drama, learns what it means to get a reputation. Some months after passively losing her virginity via some depressing house party sex -- as deftly played by Amber Tamblyn, it happens more out of disbelieving curiosity than anything else -- the high school junior becomes derisively known, not just at school but far and wide, as “the ski mom,” after giving birth to what may or may not have been a stillborn child while on a class trip to the slopes.

Forensic psychologist Lydie Crane (Tilda Swinton, glittering with sad intelligence) has gained a reputation of her own: “I wish people would stop smiling at me,” she groans. Seven months pregnant, Lydie must field the freighted well-wishing of her friends and colleagues, all of whom are aware that her last pregnancy ended with the stillbirth of an infant girl. She’s the one who lost the baby. Lydie is assigned to give Stephanie a psychological evaluation to determine the truth before her trial proceeds, and the film, which dips into flashbacks for Stephanie’s story and pulls a tight, binding stitch between the present-day lives of the women, is built around the videotaped conversations they have in Lydie’s office. The dueling dynamics between the two characters (obliged to fall into the role of teen and adult, subject and object, they can’t help relating as two women, two mothers -- a would-be and a maybe-was) are a challenge the actresses meet with riveting success.

Front-loaded for circumstantial pathos, Stephanie Daley is restrained with its dramatic currency, if sometimes frivolous with penny-dropping symbolism (sphinx-like cats are everywhere, beeper babies are handed out as a class assignment and a dreamy deer seems to die along with everyone’s innocence). Brougher’s camera follows its subjects closely as they negotiate the social and private spaces of what looks like a small, upstate town, lousy with trees and pick-up trucks. Stephanie, pale, sad-eyed and secretly boy-crazy, uses her honest face to hide all manner of turmoil; in a locker room scene Tamblyn expertly demonstrates the feat every self-conscious girl learns almost by instinct, that of changing your clothes without revealing a slip of skin. Just what Stephanie was conscious of is never clear, and the insularity of her teenaged world is supported by a very complex, very adult infrastructure of denial; her parents, whose marriage seems to be quietly, if deniably, falling apart on the margins, are exhibits A.

No stranger to denial, Lydie and her husband Paul (Timothy Hutton) are sidestepping the fact that Lydie may be more afraid of having the baby than she is of losing it, and that Paul is very likely stepping around with a woman who wears diamond stud earrings. “No one has a baby without going a little crazy,” Lydie’s friend says by way of offering both comfort and the central idea of the film; the ripple effect caused by a pregnancy sometimes overshadows (or even denies) the heavy burden of the source. In recognizing the lingering signs of that unresolved burden, Stephanie comes to trust Lydie, and the film becomes less about whether Stephanie actually murdered the child during the terrifying birth scene, which takes place in a public restroom stall. What is explored instead is the preciousness, the precariousness, of trust in our lives, as epitomized by that physical, spiritual limbo known as pregnancy, when women must trust their boyfriends, their husbands, and their own bodies not to betray them. “What if what I believe turns out not to be true?” Stephanie asks, in revisiting the day of the birth. “Then stop believing it,” Lydie replies.

By remaining physically and emotionally attuned to her actors (as they are, in turn, to their characters) and not simply the considerable melodramatic heft of her story, Brougher avoids the towel-wringer this unfortunately topical story could have been had it been called, say, The Ski Mom. Between Swinton’s wounded, watchful eyes and Tamblyn’s soft internality emerges something that transcends the inherently stale nature of their transactions; it’s an understanding far more satisfying than Stephanie’s final, somewhat canned revelation. A truth, if you will.