Atonement is set during the summer of 1935, Dunkirk in 1940 and London in 1999. Alongside Knightley, McAvoy and Garai will be newcomer Saoirse Ronan, playing the pivotal role of the fledgling young writer 13 year old Briony Tallis, who dramatically changes the course of all their lives when she accuses her sister’s lover of a crime he did not commit.