Rooney Mara and Jack Reynor in "Secret Scripture"

For what seems the longest time, you wait to hear Rooney Mara speak in “The Secret Scripture.” Like a modern-day Greta Garbo, the anticipation only builds as you see Rooney’s Rose McNulty in flashbacks as her present-day counterpart (Vanessa Redgrave) begins to reflect on how she wound up at St. Malachy’s asylum in Belfast, on the verge of being transferred away from the only home she’s known for the past 50 years. Extraordinarily fragile, the Rose we see today is indeed decades away from the stoic young woman we see arriving to work at her aunt’s temperance hotel, kept to herself even as every bachelor in town, including conspicuously the town’s priest (Theo James) and a rakish RAF pilot (Jack Reynor), has their eyes on her. Yet director Jim Sheridan, in adapting Sebastian Barry’s novel with co-writer Johnny Ferguson, knows that creating suspense rests on figuring out what’s going on in Rose’s head, with banal chit chat only likely to chip away at the mystery he painstakingly sets up. By the time you finally hear Mara talk — naturally a soft thank you when she gets off the bus in Sligo — it’s enough to leave the audience hanging on every word that comes after.

“The Secret Scripture” works best when it feels like a film from the era that it’s set in, unapologetically melodramatic and utterly in thrall to the star at its center, bending itself to the strengths of its lead rather than the other way around. Mara’s elusive quality as an actress, weaponized in “Carol” and used to full effect here, makes Rose appropriately bewitching to the men who fall over themselves to court her and enigmatic to an audience, as it’s gradually revealed why she’s at St. Malachy’s, held responsible for the murder of her newborn baby. In older age, Rose is evaluated by a psychiatrist (Eric Bana) before being moved to a new facility, her memory confined largely to what she’s scrawled in her copy of the Bible after electric shock therapy wipes away most of her consciousness, but being not much more forthcoming in her twenties for entirely different reasons, she is virtually held prisoner long before being committed, subject to the whims of men who take her refusal to engage with her as reason to exert their will.

It’s fertile territory for Sheridan, returning to a time just after the one he so vividly depicted in the 1930s-set “The Field,” where the influence of the Catholic Church can be felt throughout Rose’s life, even if she’s largely unaware of it, and his strong grasp on other period details are continually enriching. The tragedy that befalls Rose is shared by the entire country as it is beset by war, a weight that the writer/director ably carries. However, “The Secret Scripture” is burdened by an overly complex structure, toggling back and forth in time, that doesn’t do it many favors, from a overly complicated opening sequence that flashes between the past and present without supplying much context and the subsequent handoffs between Redgrave’s Rose and Mara’s feeling more mechanical than fluid. Stylistically, the two sides of the story, both compelling in their own right, never feel entirely comfortable sitting side by side and the usually dynamic Bana gets saddled with the thankless expository task of serving as the good doctor whose job it is to put all the pieces together.

Still, there’s more than enough that’s worthwhile in “The Secret Scripture,” which is driven by strength of Mara and Redgrave’s performances and the fascinating character they both get to play. In their able hands, Rose strives to create a home in her own mind away from a world that’s been far too harsh, a place that constantly intrigues as the circumstances around her change and the years go by. In even the smallest expressions of this freedom, whether it’s a rare grin from Mara or Redgrave playing a few bars of “Moonlight Sonata,” “The Secret Scripture” soars.

“The Secret Scripture” does not yet have U.S. distribution. It will play twice more at the Toronto International Film Festival on September 16th at noon at the Ryerson and September 18th at 9:45 am at the Isabel Bader Theatre.