Atonement is a complex novel told from several points of view and divided into four parts.

Part one

The story opens on a hot summer day in 1935. Precocious but naive aspiring writer Briony Tallis, aged 13, has written a play for her brother Leon, with the characters to be played by her cousins, 15-year old Lola and 9-year old twins Jackson and Pierrot.

Briony's sister, 23-year old Cecilia Tallis, has returned home from university and is confronting her confused feelings towards Robbie Turner, son of the housekeeper, whose studies were financed by Jack Tallis and who, like Cecilia, studied literature at Cambridge University. While trying to water some flowers, the couple break a valuable vase and pieces fall into the fountain. Cecilia strips to her underwear and jumps into the fountain to retrieve the fragments in front of a startled Robbie. Briony witnesses the ensuing moment of sexual tension from an upstairs bedroom and is confused as to its meaning.

Leon Tallis arrives with his friend Paul Marshall, an aspiring businessman who plans to sell chocolate bars to the Army. Leon invites Robbie to dinner, much to Cecilia's annoyance, as she is still confused as to why Robbie disturbs her so much.

Robbie, meanwhile, returns to his bungalow to write a letter to Cecilia. After finishing it, he adds a lewd suggestion on to the bottom, using the word cunt. Although he then writes another version of the letter to give to Cecilia, it is the first that is inadvertently delivered to Cecilia via Briony, who reads it and is convinced, in her fertile imagination, that Robbie is a "sex maniac". Upon reading the note, Cecilia realises her love for Robbie, and they declare their love for each other in a heated encounter in the library. Briony interrupts their lovemaking, which she interprets as a sexual assault upon her sister.

During dinner, the twin cousins run away, leaving a letter, and the family party begins searching for them in the extensive grounds of the estate. In the dark, Briony comes across Lola being raped by an unknown attacker. Briony convinces herself that the rapist is Robbie, and Lola acquiesces to this claim. The police arrive to investigate, and when Robbie arrives with the rescued twins, he is arrested solely on the basis of of Briony's testimony. Apart from Robbie's mother, only Cecilia believes in his innocence.

Part two

The reader follows Robbie Turner in France during the Dunkirk evacuation of 1940. As a result of Briony's accusation, Robbie spent three years in prison before being released on condition of enlistment in the army. He has been in contact with Cecilia, and she has promised that she'll wait for him. They've met only once since his arrest, a fleeting half hour spent in awkwardness, but they shared a kiss before Cecilia had to leave. At the end of part two, Robbie is still in Dunkirk, his fate unknown.

Part three

Briony is now working as a trainee nurse in London during the weeks leading up to and following the Dunkirk evacuation. She now believes that it was Paul Marshall who raped Lola in 1935 and feels guilty for accusing Robbie. In this section, it becomes apparent that Briony sees her nursing work as a kind of atonement; she effectively sent Robbie to a horrible war, and now she has given up her hope of attending university and is nursing soldiers. In a crucial scene, Briony pretends to be a girl from the village of a very young French soldier who has been fatally wounded and who dies in her arms. Briony also attends the wedding of Lola and Paul Marshall but lacks the courage to speak out against the marriage. She then tracks down Cecilia and promises that she will try to atone for what she has done. Robbie is with Cecilia at the time, and together they outline the legal procedures Briony will need to follow in order to exonerate Robbie.

Part four

The fourth section, titled "London 1999", is written from the perspective of Briony, now a successful novelist in her 70s. She is dying from vascular dementia. It is revealed that she is the author of the preceding sections of the novel, which are to be published only after the deaths of Lola and Paul Marshall. In the last few pages, we learn that, although they are reunited in Briony's novel, Cecilia and Robbie were never reunited in reality: Robbie died of septicaemia on the beaches of Dunkirk (most likely a result of infection from a piece of shrapnel which embeds itself in his stomach and that is mentioned many times during Part Two); and Cecilia was killed in The Blitz. Though the detail concerning Lola's marriage to Paul Marshall is true, and though Briony's narrative is evasive, it seems that she never visited Cecilia, who was mourning Robbie's death, in an effort to make amends for her lie.

The novel ends with a meditation on the nature of atonement and authorship. The conclusion that Briony appears to reach is that no amount of authorial fantasizing (or, for that matter, wretched work as a nurse) can actually atone for the crime she committed as a child of 13. The ending attempts to consider differing forms of fiction -- both lies in reality and in novels -- and suggests that while the one can be irrevocably destructive, the other can offer a chance at happiness unachievable in life.

Objects and places of significance

The Trials of Arabella

The Trials of Arabella is a play written by Briony Tallis in 1935 with the intention to teach her brother Leon to be more serious when it came to relationships. The play inevitably never gets performed due to the lack of cooperation of Jackson and Pierrot, and the further complications that follow. The Trials of Arabella is later performed in 1999 during Briony's 77th birthday by various young grandchildren.

The Tallis Estate

The Tallis Estate is located in the Surrey Hills in England, being the family home and also the site of the Tallis family party for Briony's 77th birthday. It is at The Tallis Estate that the key moments of the exposition of the story take place. The first part of the book completely takes place on this estate.

The vase

The vase is an important motif in the book. It originally belonged to Mr Tallis's brother, who received it as a present for saving the inhabitants of a town near Verdun during the first World War. Although it is very valuable, the Tallis family decides to keep using it, thus honouring its owner's memory.

The vase causes the first “real” encounter between Cecilia and Robbie (who seemingly keep ignoring each other since their return from university), when, by the fountain, they fight over the vase and break off some shards, and Cecilia undresses to get them out of the fountain. This incident also leads to (the different versions of) Robbie's apologetic letter. The subject of the vase comes up again when Briony visits Cecilia and Robbie and mentions that the vase has been broken; Cecilia is clearly unsettled by the news.

Dunkirk

The second section of the book contains detailed descriptions of the Dunkirk evacuation, in which Robbie takes part, and gives an impressive account of his war experiences.

In the fourth part, Briony is shown gathering information and obtaining opinions about the war in order to give as realistic a description as possible in her book.

The hospital

Both Cecilia and Briony become nurses and are trained at the same hospital in London. Briony (who could have had a comfortable student life at Cambridge) presumably chooses hard and lowly work to atone for her wrongdoing. In the hospital, Briony comes in contact with the harsh reality of war, and, some experts may argue, the hospital represents Briony finally growing up to the realisation of her mistakes.