13 year old Briony has a crush on Robbie, who is in love with Briony's sister Cecilia. Briony discovers Robbie and Cecilia having sex in the library. The same night two boys who visit the family run away. During the search party Briony's cousin Lola Quincey is assaulted. Briony accuses Robbie, who is arrested and convicted. Robbie gets a chance to get out of prison if he goes to war.