Epic period piece spanning 65 years, starting in the 1930s England.

Rating: Null/10 (4 April 2008)

Atonement: compensation for a wrong.
The story is not always linear, but in total spans from around 1934 when Briony Tallis, future author, is around 11, to around 2000 when she is 77, dying, and announces that she has written her last of 21 novels. She says, in a real sense, it is her first since she began thinking of it since she was a young girl.
The movie is made mostly from Briony's perspective. Saoirse Ronan is Briony Tallis at age 13, living in a mansion in rural England in 1935. Her older sister is Keira Knightley as Cecilia Tallis. The third member of the "love triangle" is James McAvoy as Robbie Turner, son of the Tallis household's maid. He is treated much like a family member and even his schooling is financed by them. His mother is Brenda Blethyn as Grace Turner.
Briony is smart and demanding, and fashions herself as an author, writing her first play at 13. But she also is secretly in love with Robbie who just treats her as a younger sister. We see a flashback to when Briony was 11 or 12 (her words) and she jumps into a pond to have him "save" her.
But Robbie and Cecilia are the ones who really are falling in love with each other. Something happens at a fountain, Briony sees it from afar, doesn't understand what happened, and comes away with a bad feeling against Robbie, partly because in her young mind feels cheated by him. So, when something else comes up later that evening, she takes it out on Robbie and it has a lasting affect.
So the rest of the movie is about Briony eventually learning the truth, and doing what she can for atonement, trying to make right her wrong. Good movie, even touching on the conflicts in France in the early 1940s part of WW II.
August 2013 update: I just watched it again, it is better than I had remembered it, very good on repeat viewing.
SPOILERS: Briony's wrong was naming Robbie as the man she saw that night apparently raping a teenage house guest in the field. As a result Robbie was imprisoned, and after 3 1/2 years got out only because he agreed to enlist in the Army and fight. So his and Cecilia's romance was effectively ended. But later Briony found that the "rapist" and the teenager got married, meaning it probably wasn't a rape at all. Unfortunately both Robbie and Cecilia, now a nurse, both died as a result of the war, but in "atonement" Briony gave them happiness and a life together in her final book, "Atonement", that was the only gift she could give to them, after their deaths.