The entirety of Ian McEwan's novel unfolds on February 15, 2003 — the day two million people march through London against the impending invasion of Iraq, the largest demonstration in British history. Neurosurgeon Henry Perowne drives through streets full of marchers, has a minor car confrontation that escalates into something dangerous, and returns home to a family dinner that ends in violent intrusion — the question of the war he cannot resolve hanging over everything.