Faith is 24 hours of doubt and one minute of hope, claims one of the sisters in Anne Fontaine's (Coco Before Chanel) compelling and powerful French-Polish drama.

Based on real events, The Innocents is set in the bleak, snow-covered landscape of postwar Poland, in December 1945. Much of the film is shot within the cloistered walls of a Benedictine convent, which initially presents as a place of sanctity and serenity.

The film's protagonist, Mathilde (Lou de Laâge), is a young French doctor working with the Red Cross. When a nun runs into a hospital begging for help, Mathilde defies protocol and accompanies her to the convent where she discovers another nun in labour. She soon finds out that several other members of the order are pregnant, all victims of assault by Russian soldiers. "I can still smell their odour," one of the sisters later tells her. Within their fiercely private world, Mathilde becomes their only hope.

Rational, resilient and compassionate, Lou de Laâge shines as Mathilde. Brief love interest comes in the form of her superior, Samuel, a Jewish doctor whose wry comment, "There are a few of us left," is one of the reminders of the subtle shadow of the Holocaust.

Despite their outward, identical appearances and common communal purpose, the nuns' individual characters, personal stories and attitude to faith distinguish each from the other. There is contrast too between the melodic religious ritual and routine of the nuns with the pain of pregnancy and birth. Many are unable to reconcile the brutality that they have suffered with their faith and we experience their anguish and self-torment. Those who are more worldly, such as Sister Maria (Agata Buzek) with whom Mathilde strikes an alliance, are better able to manage the trauma.

Amid a climate of fear and shame, there is conflict played out between the notably resolute and steely Mother Abbess (Agata Kulesza, "Ida") and Sister Maria. Above all, the Abbess believes that her duty is to protect their secret, with unbearable consequences.

Visually stunning, The Innocents has an almost painterly quality to it. But at times it is harrowing viewing. Apart from a too tidy ending that errs on the sentimental, this is a superbly cast, standout film about the fragility of faith, which is difficult to let go.