Director Pascal Laugier has gone on record apologizing for "Martyrs," and he was only partially joking. This is not to suggest that he thinks he has made a bad film, but one that works all too effectively, daring to go to places so despairing and bleak that few prospective viewers will be able to aptly prepare themselves. Indeed, one cannot passively watch "Martyrs;" it is too strong, too bold, and too thematically loaded for apathy. For those who would prefer a cinematic walk through the proverbial park, look elsewhere. All others willing to go on an experience that transcends the unthinkable, gird your loins.

When Lucie (Mylène Jampanoï) was a child, she was abducted and held captive for a year, facing daily physical abuse before narrowly escaping with her life. The people responsible were never apprehended. Sent to live at a youth home during her recovery, she is befriended by the compassionate Anna (Morjana Alaoui). Although Lucie is safe, she is unable to escape from her terrifying traumatic memories caused by the experience. Fifteen years later, a seemingly normal family—a mother (Patricia Tulasne), father (Robert Toupin), son (Xavier Dolan) and daughter (Juliette Gosselin, heartbreaking)—sitting down to breakfast are interrupted by the doorbell. Standing outside is Lucie, looking to make all four members pay with their lives for the parents' sins. She is convinced they are her kidnappers from the past, but has not fully thought out her plan. When Anna arrives, she tries to take control of the situation and clean up the mess, but her attempts to help her best friend are lost on a mentally tortured young woman who will never be able to escape her past and the incontrovertible damage already done to her.

What has been described so far takes up, maybe, the opening thirty minutes of a part-ghastly, part-meditative barrier-breaker that defies easy categorization and lets no one involved off the hook. Powerfully blunt violence begets rapid-fire intensity begets a transformative second half delving into nothing less than the literal search for God. Tough to take but imminently rewarding, "Martyrs" is one of those films that is impossible to guess where it is going. Grabbing viewers, and grabbing them hard, the early moments where a family sees their loved ones and their own life systematically wiped out in a flash is petrifyingly authentic. The more one learns about them, though, the more it becomes apparent that looks are most definitely deceiving. From there, Laugier plows forward, his sympathetic if uncompromising handling of the characters making the horror elements all the more impactful. He knows exactly where he is headed, and he doesn't dare disclose it's happening on the screen.

For much of the film, Morjana Alaoui and Mylène Jampanoï are front and center, carrying the twisty narrative to places forbidding and austere. These are demanding roles in all conceivable senses of the term, and the bravery with which the actors approach the harsh realities of their protagonists' circumstances is not to be marginalized. As Lucie, Jampanoï heads up the first act, the flurry of emotions she goes through—grief, shame, rage, terror—tipped over by haunting hallucinatory visions of the malnourished, mutilated fellow victim she left behind all those years ago. Alaoui, as Anna, is given an even more demanding task, baring her soul as nakedly as she does her body. In a key supporting turn that fiercely haunts the picture's closing moments, Catherine Bègin portrays Mademoiselle, an aging woman willing to go to extremes to find out whether or not there is something beyond the physical plane of life.

Harrowing and unforgettably ambiguous in its final stretch, the French-Canadian "Martyrs" (it was filmed in Québec) yanks the viewer into a world both unthinkably vicious and unfair, but also transcendent. If evil exists, so, too, does humanity's fear of the universe's natural process. Some people may turn toward faith as a means of coping with what they do not finitely know, while others concentrate on science. The film imagines a third group, bred out of desperation, who will do whatever it takes to know what awaits them on the other side of their last breath. Do they get their answer? The screenplay's last words, "Keep doubting," linger tenebrously in the air even after the credits have rolled. "Martyrs" is one of the loftiest achievements the horror genre has seen in the twenty-first century.