Atonement

In 1935, Briony Tallis (Saoirse Ronan), a 13-year-old girl from a wealthy English family, has just finished writing a play. As Briony attempts to stage the play with her cousins, they get bored and decide to go swimming. Briony stays behind and witnesses a significant moment of sexual tension between her older sister, Cecilia (Keira Knightley), and Robbie Turner (James McAvoy), a man Briony has a childish crush on. Robbie returns home and writes several drafts of letters to Cecilia, including one, explicit and erotically charged. He does not, however, intend to send it and sets it aside. On his way to join the Tallis family celebration, Robbie asks Briony to deliver his letter, only to later realise that he has mistakenly given her the prurient one. Briony secretly reads the letter and becomes still more suspicious of Robbie's intentions.

That evening, Cecilia and Robbie meet in the library, where they spontaneously have sex. During the act, Briony walks in on the couple and mistakenly believes that Robbie is raping her sister. At dinner it is revealed that the twin cousins have run away. Briony goes off alone into the woods looking for them and stumbles upon a man running away from apparently raping her teenaged cousin Lola (Juno Temple). Lola claims that she does not know the identity of her attacker, but Briony is certain that it was Robbie, and tells everyone this, including the police, claiming she saw Robbie commit the act. She shows the shocking letter to her mother. Everyone believes her story – except for Cecilia. Robbie is arrested and sent to prison.

Four years later, Robbie is released from prison on condition that he join the British Army. He is assigned to A Company, 1st Battalion, Royal Sussex Regiment. He is reunited with Cecilia in London,who does not speak with her family after the incident and lives alone in London, where they renew their love before he is shipped off to the French front. Briony (Romola Garai), now 18, has joined Cecilia's old nursing corps at St. Thomas's in London because she wants to be of some practical use to the society and has given up an offer she received from Cambridge. Her attempts at contacting her sister go unanswered, as Cecilia blames her for Robbie's imprisonment. Later, Robbie, wounded and very ill, finally arrives at the beaches of Dunkirk, where he waits to be evacuated.

Briony, now fully understanding the impact of her accusation, later visits Cecilia to apologize to her directly. Cecilia coldly replies that she will never forgive her. Robbie, in a rage that almost becomes physical, confronts Briony and demands that she immediately tell her family and the authorities the truth. Briony reveals that the rapist was actually family friend Paul Marshall (Benedict Cumberbatch), who was an adult at the time of the rape, and that he cannot be implicated in a court of law because he has married Lola.

Decades later, an elderly Briony (Vanessa Redgrave) reveals in an interview that she is dying of vascular dementia, and that her novel, Atonement, which she has been working on for most of her adult life, will be her last. Briony reveals that the book's ending where she apologized to Cecilia and Robbie is fictional. In reality, Robbie actually died at Dunkirk of septicemia while awaiting evacuation, and that Cecilia died a few months later as one of the flood victims in the Balham tube station of the London Underground during The Blitz. Briony hopes that, by reuniting them in fiction, she can give them the happy conclusion to their lives that they have always deserved.