England And France, 1935 To 1999
Yeah, that's a lot of setting included right there. Luckily, everything doesn't happen everywhere at once, which would be confusing both in the book, and in real life. So, let's see where the homeys at. First, at home:
The Tallis Home
The Tallises are not exactly stinking rich, maybe, but they are pretty darn rich. They've got servants; they've got a pool; they've got gardens and a fancy fountain and grounds big enough that they need to send out search parties when Jackson and Pierrot wander off.
The whole first section of the novel is set at the house in 1935, before World War II. The setting is idyllic (who wouldn't want to live in a giant house with servants to do your gardening?) and also fragile (like the vase Robbie and Cecilia break). The war is coming, like the "black-furred creature" of Emily Tallis's migraine (1.6.3), and everyone's dreams for the future—not just Robbie's and Cecilia's—are going to shatter.
After the first part of the book, we learn bits and pieces of what happens to the Tallis home. During the war, the Tallis family has to take in refugees from London and elsewhere who are fleeing the upcoming German air strikes (the Blitz). And finally, in the last section set in 1999, the Tallis home has been converted into a hotel. Which gives you an idea of how mega-honking-huge it is.
France And Dunkirk
The second part of the novel is set at the end of May, 1940 in France just after the British Expeditionary Force has had its butt kicked by the Nazis. The BEF is retreating to Dunkirk on the French coast, where they're hoping they'll be picked up and transported back to England.
Dunkirk is often presented as a triumph of sorts. The British government asked individuals with boats to help with the evacuation, and thousands of people with small crafts responded, helping rescue thousands of soldiers.
In Atonement, however, Dunkirk is a giant, chaotic, steaming pile of mess. British soldiers are wandering haplessly around the countryside. The Royal Air Force (RAF) is nowhere to be found, and German fighters drop bombs on tired, hungry, retreating soldiers at will. Officers issue ridiculous orders and there's no food or water. The retreat is less a courageous example of pluck, and more an ill-planned devastating defeat.
The setting itself, and all its "unexpected detail" (2.1)—the boy's leg in the tree, the troops attacking the RAF officer—serves as a kind of criticism, or parody, of Britain's self-image and self-mythology. In a similar way, it contrasts with the first part of the book, where the Tallis family home is supposed to signify both their wealth and the security that supposedly comes with it.
This is also the setting where McEwan gets to get gory and grimy and show you dead bodies and severed limbs and veins in your teeth. McEwan was known as "Ian Macabre" for a while because his early books had yucky details like that. Atonement is much less horror-filmy, but maybe McEwan wanted to throw in just a little gore for his old-school fans.
The third part of the book is set in London, mostly in the hospital where Briony works. Again, here we get to see the horrors of war, this time as wounded soldiers stream in with terrible wounds. This is also the section where we see, by letter, glimpses of Emily Tallis complaining about having to deal with evacuees. The contrast between happy idyllic rich people upset because their gardens are being trampled on and soldiers getting their limbs blown off is not subtle—but hey, who wants subtle all the time?