The slow, atmospheric opening sequences of "Atonement," taking place on a hot summer day in 1935, recall one of those Merchant Ivory wallpaper movies, with panoramas of rolling meadows, long shots of a large mansion, and inside, the camera stroking the wainscoting and fondling the furniture. The Tallis family, especially the precocious 13-year-old Briony (Saoirise Ronan) and her sister Cecilia (Keira Knightley), a recent university graduate, resemble the pale, languid children of privilege who often populate those houses and those films. The languor and the oppressive air of good breeding vanish, however, in a melodrama manufactured out of Briony's pubescent jealousy and fevered imagination.

Because she reads a note that her father's lower class protégé Robbie Turner (James McAvoy) sends to Cecilia, then witnesses the couple in a sexual encounter, Briony concludes that her beloved Robbie is a "sex maniac," which leads her to accuse him of assaulting her cousin Lola. That single incident, fueled by Briony's confusion and fantasy, dooms all the people in the film, transforming it from an examination of a particular family into a story of ruined lives and a passion that transcends the boundaries of class and the obstacles of a tragic history.

Changing points of view, mixing present action with flashbacks and flash forwards, the movie skips over five years and picks up its action in 1940, where both Cecilia and Briony, estranged from one another by Briony's false accusation, work as nurses, caring for wounded soldiers. Released from prison to serve in the army, Robbie, part of the routed British Expeditionary Force in France, makes his way across the countryside to join the great retreat to Dunkirk. His memories and dreams fill in the gaps in the narrative, revealing the pattern of the life that Briony essentially created for him and Cecilia.

The title refers to Cecilia's interpretation of Briony's nursing studies, which she believes represent an atonement for ruining the lives of her sister and her lover and irreparably damaging her family. It also refers to Briony's narrative of the movie itself, the novel she writes that constitutes the substance of the film. Briony appears at the end of the picture, an aged, dying woman, a successful author (Vanessa Redgrave) interviewed on television about her latest and last novel, "Atonement," which she writes in order to expiate as well as she can for the dreadful action that doomed so many people to loss, grief, and death.

The film we see and the novel Briony writes constantly play with the meaning of fiction, confusing memory with dream, actual events with fantasies. She acknowledges the tragedies that result from that single terrible act on a hot summer night in 1935, while also creating for the lovers an illusion of happiness and fulfillment. Her explanation of her novel suggests the transformative power of art, which substitutes for the cruel, sad, inexplicable reality of human life something like coherence, beauty, and significance.

Aside from some slow and soggy stretches in its second half, "Atonement" generally covers a great deal of ground with a pleasing efficiency, achieving the effects of its sometimes convoluted story with a rare combination of subtlety and clarity. Through its attention to the details of its places - the Tallis house, wartime London - it convincingly reflects the reality and spirit of its times. A long set piece, a remarkable panorama of the beach at Dunkirk, with thousands of soldiers waiting and hoping for rescue, killing their horses, disabling their vehicles, drinking, singing, and, yes, dying, recalls the most famous shot in "Gone With the Wind," the immense crane shot of the wounded and dying in Atlanta.

Lithe and wan, Keira Knightley smolders with the passion of a repressed young woman awakened to her sexuality by the embarrassed eroticism of her lover. James McAvoy, on the other hand, seems even more soppy than the usual British leading man and certainly not terribly convincing as the virile working-class lad so adored by a generation of English writers. Saorise Ronan, who plays the young Briony, projects both innocence and malice, displaying an intensity and intelligence that nicely epitomizes the emotions and meanings of "Atonement."

Atonement

(R), directed by Joe Wright

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