I have not read the novel that this was adapted from, so several of the revelations, especially toward the end, were news to me. And it turned out that the two people I saw it with, both of whom had read the novel, liked the movie better than I did, so it may be a case where the movie works better for those familiar with the source material than those who aren't. Or not—who knows?
The deal is as such: It's 1935 England, and Keira Knightley is Cecilia Tallis, living in a fancy house with her parents and little sister Briony. In the opening moments, we see Briony finishing a play she's written, the taps of her typewriter forming part of the overbearing musical score. She looks out the window and sees Robbie, played by James McAvoy, with Cecilia, out by the fountain. Ceclilia strips down to her underwear and jumps in, then emerges and stands for a moment in front of Robbie, all wet and revealed. 13-year-old Briony is a little shocked.
Then we see the same event from Cecilia and Robbie's perspective. In flirting, a vase broke and a piece fell in the fountain; Cecilia jumped in to get it. What appeared somewhat menacing to Briony was actually quite flirtatious, and made Cecilia and Robbie really hot for one another. Robbie is invited to dinner that night, and writes a few notes to Cecilia, giving it to Briony to deliver in advance of his arrival. He remembers when it's too late that he gave her the wrong note—the one delivered was an earlier draft that expresses his wish to perform vigorous oral sex on Cecilia, particularly calling out her CUNT! Of course, Briony reads the letter before giving it to Cecilia, and she and Lola, a detestable little girl who has arrived with her detestable little brothers, discuss it and decide that Robbie must be some sort of sex maniac.
So Briony goes downstairs and is drawn into a study, where she sees Cecilia and Robbie fucking against the wall, and again it looks somewhat sinister. We then see the same event from the adult's perspective, which is that they had both declared their love for one another and went at it, nothing sinister about it. One thing that is either an error or something I don't understand the meaning of is that in Briony's version, the door is clearly ajar, while in the adults' version, they quite clearly close the door behind them. In here we also have a flashback that indicates that Briony has a crush on Robbie.
MINOR SPOILERS > IF YOU KNOW ABSOLUTELY NOTHING ABOUT THIS MOVIE, YOU MIGHT WANT TO SKIP TO THE END NOW > > >
So it turns out that Lola and her horrid brothers have run away, which seems like cause for celebration, but everyone mobilizes to look for them. I forgot to mention that Cecilia's brother and one of his friends are also present. Biony finds someone being sexually assaulted, and catches a shadowed glimpse of someone running away. In her mind, it is Robbie, and she tells her parents and the police so, producing the note he wrote. Robbie is sent to prison!
Four years later, Robbie is involved in the war [he could choose to join the army or stay a prisoner]. Cecilia is a nurse. There's lots of war stuff—which I have to say seems almost completely irrelevant in retrospect—and at one point he and Cecilia meet for about five minutes in a café. This is one of the strongest scenes in the film—it will definitely be James McAvoy's Oscar clip—as they try to remain calm but are obviously simultaneously overjoyed to see each other and heartbroken at what's happened. Then Robbie goes back to war and so does Cecilia.
They write to each other. Robbie has some war adventures, including the much-discussed long tracking shot on a beach where all sorts of surreal goings-on happening, although again, in retrospect I can't see what this had anything to do with anything. Except that war is hell, of course. We soon meet Briony as an 18-year-old, played by the fantabulous Romola Garai, who charmed the pants off me in Dirty Dancing: Havana Nights, and I fully suspect will be charming me for years to come. She now realizes what she did, and wants to meet with Cecilia to explain. They meet one day, she says she's sorry, and then Robbie comes out of the bedroom. They make arrangements for Briony to write letters clearing Robbie's name, and Briony says she's sorry. Then it's back to war for all of them!
MEGA-SPOILERS NOW > HERE THE ENDING OF THE FILM IS REVEALED > > >
Some more bullshit happens, then suddenly it's years later and Briony is played by Vanessa Redgrave. She's a successful novelist, and is being interviewed on a talk show about her latest and final novel, called Atonement. She reveals that the novel is a way for her to atone for the past, but also a lie—because she never met with Cecilia and Robbie, because actually, they had both been killed in the war by then. And she had never cleared their names, she never did anything but live with it. So the last part of the movie that we've just seen was all her novel.
This makes a lot of sense—this is why we had so much of the typewriter clacking on the score: because Briony was writing her novel this whole time. This also makes sense of why in some of the scenes one can't tell if it's really happening or if it's in Briony's mind, like when Robbie appears in Cecilia's apartment. At first it seems like Briony is just imagining it and—turns out she is! Some of the reviews I've read pull out meanings such as how Briony's life was ruined by her secret [although with 21 successful novels to her name, I'd wouldn't mind if my life was ruined like hers—although she did apparently spend 80 years of her life without once changing her hairstyle], the relationship between the truth and art, between true stories and novels, how we can never really atone for anything—and maybe I'm just thick, but none of that came out of the movie for me. My suspicion is that these critics are transposing the meanings they gleaned from the book onto the movie, like I think my friends did, because it seems to me that if you go by what is on the screen alone, not that much made it here.
< < < SPOILERS END
It was all very tepid and removed. I found both the directorial style and the music to be overbearing from the start, both of which distanced me from getting involved with the story. Of course we later find out that there's a reason for this, but by then it's too late. Ironically, I think the movie would have been stronger had they not included all of those stylistic clues as to what was happening throughout. That is, it supports the final revelation, but undermines the entire movie before it, in the process draining the fizz from the revelation. The other thing is that since the first 30 minutes are so involving, the rest of the movie can only come off as tepid and meandering. In retrospect, I really can't see why we had to sit through all that war stuff in the middle—except that maybe it worked in the book. The structure also leaves one with the feeling that our main characters are abandoned somewhere near the beginning and we never really see them again, despite the fact that they're on screen most of the time. And as for the sense of what Briony's life turned out to be, well, it's going to take more than a five minute speech at the end, despite Vanessa Redgrave's considerable efforts.
Both Knightley and McAvoy are downright brilliant. Keira Knightly bugs me—I just don't like the whole blasé look she gives off, but she's usually good in the movies themselves, and I've never seen her be better than she was here. Her character is brittle and reserved, but very passionate underneath, and it all comes out here in her quick bursts of quickly-spoken, perfectly-enunciated dialogue. McAvoy comes off as much more handsome and charming than he was in Last King of Scotland, and like I said, his scene in the cafeteria is a tear-jerker and makes you wonder at his acting skills. Everyone else is good, too. The whole thing looks great, it all flows smoothly, it's just that afterward, looking back and knowing it all, the entire middle hour seems rather pointless. One can see where this would have worked in the novel, as the main revelation is really an idea that gives a context to the character's history, which is hard to capture on film. Compare this with the ending of The Sixth Sense, which had a revelation that gave context to the film's EVENTS, which were things one witnessed and vicariously experienced, so they're much more concrete than the things that need rethinking here. Alas, the effort is there, but the results sadly aren't.
It won't hurt, but I think you'll get a lot more out of it if you've read the book.