Thirteen-year-old fledgling writer Briony Tallis irrevocably changes the course of several lives when she accuses her older sister's lover of a crime he did not commit.
When Briony Tallis (Saoirse Ronan), thirteen-years-old and an aspiring writer, sees her older sister Cecilia (Keira Knightley) and Robbie Turner (James McAvoy) at the fountain in front of the family estate, she misinterprets what is happening, thus setting into motion a series of misunderstandings and a childish pique that will have lasting repercussions for all of them. Robbie is the son of a family servant toward whom the family has always been kind. They paid for his time at Cambridge and now he plans on going to medical school. After the fountain incident, Briony reads a letter intended for Cecilia and concludes that Robbie is a deviant. When her cousin Lola (Juno Temple) is raped, she tells the Police that it was Robbie she saw committing the deed.—garykmcd
In 1939, Robbie Turner (James McAvoy) is a Private in the British Army, he and his battalion who are heading to France to fight in the war. A stint in the army is not where his life was headed, which took a radical turn four years earlier at the Tallis estate where he grew up as his mother worked as the Tallis' live-in housekeeper. As such, he grew up with the three Tallis children: son Leon (Patrick Kennedy), and daughters Cecilia (Keira Knightley) and Briony (Saoirse Ronan). Robbie and Cecilia were just getting to the stage of their lives of being able to confess their true love for each other. But then thirteen-year-old aspiring writer Briony also had a crush on the older Robbie. Based on two incidents she saw between Cecilia and Robbie (one only from afar), on reading a private letter Robbie wrote to Cecilia, and on her own feelings for Robbie, Briony told some truths and half-truths about Robbie which resulted in this turn in his life. Robbie is able to reconnect with Cecilia before he is shipped off to France, and lives only to be able to head back to London to be with Cecilia and make up for the missing four years they could not spend together due to Briony's actions. A year later, Briony (Romola Garai), now eighteen, also arrives in London to start working as a nurse to support the war effort. By this time, she is aware of the damage her thirteen-year-old self caused, and wants to atone for that error to Cecilia, from whom she has been estranged, and Robbie, who she has not seen since. She will make this atonement even if neither Robbie or Cecilia will ever speak to her, or if it takes the rest of her life.—Huggo
The day that thirteen-year-old Briony Tallis (Saoirse Ronan) came across her older sister Cecilia (Keira Knightley) and her lover Robbie Turner (James McAvoy) making love in the library was a day that would have repercussions for all three of them. Briony misunderstands what has taken place between them and her reaction later tears the two lovers apart perhaps forever as war breaks out in Britain.—mel47
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 servant's son, a man that Briony has a childish crush on. Robbie returns home and writes several drafts of letters to Cecilia, including one that is 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 realize that he has mistakenly given her the prurient draft. Briony secretly reads the letter and is simultaneously disgusted and jealous.
That evening, Cecilia and Robbie meet in the library, where they make love and then confess their love for one another. During the act, Briony watches through the partially open door and her confused emotions about Robbie become heightened. 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 teenage cousin Lola (Juno Temple). Lola claims that she does not know the identity of her attacker. In a fit of pique the still-hurt Briony tells everyone, including the police, that she saw Robbie commit the act. She shows Robbie's shocking letter to her mother. Everyone believes her story except for Cecilia and Robbie's mother. Robbie is arrested and sent to prison.
Four years later, Robbie is released from prison on condition that he join the army. He is assigned to A Company, 1st Battalion, Royal Sussex Regiment. He is reunited with Cecilia (who has not spoken with her family since the incident) 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 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 consequences of her accusation, later visits the now-married Cecilia and Robbie to apologize to them 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 admits that the rapist was actually family friend Paul Marshall (Benedict Cumberbatch), but 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. Cecilia and Robbie never saw each other again once he left for war.
In reality, Robbie actually died at Dunkirk of septicemia while awaiting evacuation, and Cecilia died a few months later as one of the flood victims in the Balham tube station bombing during The Blitz. Briony hopes that, by reuniting them in fiction, she can give them the happy conclusion to their lives that they had always deserved. The last scene of the movie has Cecilia and Robbie once again together in what could be a fictional plane of existence.
