Thomas shines as a woman haunted

Kristin Scott Thomas (right) with Elsa Zylberstein in ''I've Loved You So Long.'' (Thierry Valletoux/Sony Pictures Classics)

In "I've Loved You So Long," Kristin Scott Thomas is like a flower opening in extreme slow motion. Her character, a recently paroled murderess named Juliette Fontaine, is drab and desiccated when we first meet her - a dead thing - yet by the final frames she's fully among the living, and the transition has been so subtle it's impossible to point to where or how it happens scene by scene. It's a genuinely remarkable performance, watchful and withheld, with endless emotions compressed by the stone sitting on this woman's heart.

The rest of Philippe Claudel's film isn't quite as strong, unfortunately. A novelist and screenwriter, he's directing for the first time here, and he leans on melodramatic contrivances more than he needs to. Still, he gives us a lean and observant weepie, and the mystery of Thomas's Juliette pulls you in.

She arrives in the French city of Nancy, sprung after 15 years in prison and landing on the doorstep of her sister, Léa (Elsa Zylberstein). The latter was a teenager when Juliette was convicted, barred from communicating with her by their parents; now a married professor with two adopted Chinese daughters (Lise Ségur and Lily-Rose), Léa is a cautious bourgeoisie desperate to atone for her own crimes of sisterly neglect.

By contrast, Juliette's pressing issues are real-world: get a job, find an apartment, learn to breathe. She still carries her jail cell around inside her: the memory of her crime, the specifics of which are doled out to us in detailed crumbs. Few are allowed to reach past the bars, certainly not a nosy welfare worker (Catherine Hosmalin) or Juliette's parole officer (Frédéric Pierrot), himself a lost soul. Even Léa isn't given the keys.

Juliette only lets her guard down around those who aren't asking for anything: her older niece and Léa's father-in-law (Jean-Claude Arnaud), a grizzled, kindly stroke victim whose muteness makes him a convenient sounding board. Circling around the outskirts is Michel (Laurent Grévill), a colleague of Léa's and a flirt given gravitas by his own brushes with tragedy.

Right there you come up against the patness of Claudel's storytelling - the fact that Michel needs a dead wife in his past for him to represent a potential future for Juliette. It's present, too, in the tasteful electric guitar noodlings on the soundtrack, and in the telltale piece of paper that helps Léa solve the puzzle of her sister's crime. Things fit together neatly in "I've Loved You So Long" rather than happening of their own accord. A spookily tender scene of Juliette kissing her sleeping niece becomes just another emotional plot point when Léa moves into the background of the frame as a silent witness.

It's up to Thomas, then, to ground the film and make it matter, and this she does without strain. (If you're fluent in French and bothered by the actress's British accent, the script awkwardly explains it away as time spent in England during the character's youth.) Juliette is a ghost who's not at all certain she wants to rejoin the human world, and Thomas conveys that inner battle with eyes that suddenly veil and a mouth that can tilt in a cynical crook.

Desperation leaks through only now and then: at a dinner party where the boorish host tries to divine where she's been for 15 years, or when Léa takes Juliette to see their mother (Claire Johnston), an Alzheimer's patient for whom the parting mists briefly allow her to see the little girl in the grown woman before her.

Thomas packs infinite amounts of nuance and agony into such moments, and after a while she outraces the movie itself. By the climactic scenes of "I've Loved You So Long," when Claudel's script finally gives Juliette the explosive Big Reveal toward which the movie's been building all along, you realize the scene's not really needed. The actress has already told us everything we need to know about the never-ending hardship of burying sorrow.