The war is under way and Robbie - McAvoy ("The Last King of Scotland") brilliantly portrays him as a very changed man - has been released from prison to serve in the Army in France.
McAvoy, who made his mark in "The Last King of Scotland," here becomes a bona fide leading man, his virility in early scenes later giving way to an even more affecting sensitivity.
McAvoy ("The Last King of Scotland") comes into his own as a lead; and Knightley, costumed to the nines, gives her most mature performance to date.
Atonement will certainly make McAvoy, who was inevitably overshadowed by Forest Whitaker in The Last King of Scotland, a star in his own right.
And as Robbie, McAvoy (The Last King of Scotland, Becoming Jane), radioactive with lust, personifies Atonement's broken heart.
To put a story like this across, the actors must be in complete sync with the project and each other, and McAvoy, recently seen opposite Forest Whitaker in "The Last King of Scotland," and Knightley, whom the "Pirates of the Caribbean" movies turned into an international star, are able to do just that.