A study of marriage and motherhood

“Stephanie Daley” is the last person you’d pick to have a film with her name on it. A high school student from an unnamed small town, she’s a regular 16-year-old who plays flute in the band, the kind of shy person who goes upstairs to hide out during hot parties.

But it is Daley, exceptionally well played by Amber Tamblyn, we see in the film’s opening minutes, being rushed to a hospital after she’s made bloody footprints in the snow. Secretly -- and possibly unknowingly -- pregnant, she has given birth alone while on a school ski trip and is now charged with her premature baby’s death. It is the stuff of tabloid television, and, in the hands of writer-director Hilary Brougher, the stuff of strong, understated drama as well.

“Stephanie Daley” won the Waldo Salt Screenwriting Award at Sundance more than a year ago, and it has taken this long to reach theaters because of its controversial subject matter and the unflinching way key sections of the story are presented. Brougher has taken material that sounds contrived and potentially exploitative and used her gift for careful observation and restrained emotionality to give it surprising authenticity.

Tamblyn, best known for her work in TV’s “Joan of Arcadia,” gives a breakthrough performance that is especially impressive because it shows much while seeming to do very little. When we meet Stephanie after her baby’s death, she is more reserved than ever, as haunted and withdrawn as a ghost walker. But the sense of powerful emotions roiling behind an awkward exterior is always present, and Tamblyn gradually allows us to peer deeply into her character’s being.

Stephanie is not the only person the film takes its time bringing into focus. Lydie Crane, played by the always effective Tilda Swinton, is a forensic psychologist who, in the film’s key coincidence, is roughly as many weeks pregnant as Stephanie’s baby was when it died.

More than that, her husband (Timothy Hutton) and her obstetrician (Novella Nelson) worry about Lydia’s health because she conceived only three months after the stillbirth of an earlier child.

Energetic and committed to her work, Lydie doesn’t hesitate when the local prosecutor calls and asks her to make an unbiased evaluation of Stephanie’s mental state before a forthcoming competency hearing. More specifically, she is to try to ascertain the truth of the girl’s assertion that she didn’t know she was pregnant and that her child was stillborn.

“Stephanie Daley” proceeds to unfold on several stages. We watch what are in effect therapy sessions between Stephanie and Lydie, we see them in their daily lives outside Lydie’s office, and we witness extensive flashbacks that show the events leading up to that traumatic birth.

Though Swinton is justifiably a legend among independent artists, one of the weaknesses of “Stephanie Daley” is that sections of the film that deal with her private life, with her increasingly shaky relationship with her husband, are initially the least interesting things we see. Given how familiar high school crises are, it is a tribute to Tamblyn’s artistry and writer-director Brougher’s skills that they make Stephanie’s teenage days of greater interest than Lydie’s married life.

Gradually, however, the film achieves the balance it is looking for. Lydie and her story become an increasingly effective counterweight to Stephanie’s tale as both women, in spheres different and alike, must come to terms with actions taken in the past. Neither woman’s experience, finally, would be as effective on screen without the other’s, but together they come fully alive.

That we eventually witness Stephanie’s birth scene is something that needs to be revealed, because it is portrayed with such wrenching force that the director told the New York Times that four people have fainted at those moments at festival screenings. To see Tamblyn’s work here, to see her character almost simultaneously embody pain, terror, anguish, embarrassment, regret and just about any emotion you can think of, is to watch the kind of acting the medium exists to provide.

kenneth.turan@latimes.com

“Stephanie Daley.” MPAA rating: R for disturbing material involving teen pregnancy, sexual content and language. Running time: 1 hour, 32 minutes. Exclusively at the Regent Showcase, 614 La Brea Ave. (323) 934-2944; Laemmle’s Sunset 5, 8000 Sunset Blvd. (323) 848-3500; Playhouse Cinemas, 673 E. Colorado Blvd., Pasadena (626) 844-6500.