Briony decides she has witnessed a scene that is sinister; that Robbie has somehow forced her sister to disrobe.
In this first section of the book, the reader is treated to the spoiled world of Briony Tallis, for whom the world is a gigantic oyster. She still perceives people, life and events as they pertain to her. Though she is highly creative, she has not achieved that level of maturity to temper her ability within reason. She no more considers the consequences of her actions in accusing Robbie than she would have in taking an evening stroll. In fact, the first part of this novel paints a very disagreeable portrait of this character.
Moreover, as the second section unwinds, maturity inevitably comes, but not completely. Briony seeks to make amends for her lies, though she vows never to confess to anyone that it was a lie. Instead, she believes that if she "does well", that it will "atone" for the catastrophe which immediately followed her lie.
The majority of the story is told in multiple viewpoints, and in the second section of the book, the reader begins to get inside the head of Robbie. World War II has broken out and Robbie is on the front lines, having been released from prison. Briony, in an effort to continue her pattern of atonement, joins the war effort as a nurse's aide. This is another glimpse of the generational shift as Briony, surrounded by mangled bodies, realizes that the bodies are so easily torn and so hard to mend after all. This is symbolic of the lie which she told as a child and the lie which caused gaping wounds that refused to heal properly. Yet, she is still not at the point of realizing her inability to play God, She states at one point; "But what was guilt these days? It was cheap. Everyone was guilty, and no one was". Later in this section, Cecilia, who has always believed in Robbie's innocence leaves the family home to be with him?.
The third section of the novel continues with the winding down of the war.