In 2010, two decades after the Cold War had ended, ten Russian spies were arrested in America, having hidden their true identities from their friends, neighbours and even their children. They were part of a spy programme that had begun nearly a century earlier, when the revolutionary Bolshevik government began sending Soviet citizens abroad to pose as foreign aristocrats, merchants and students.

These deep-cover missions – some remarkable feats of espionage, others high-profile failures – could last for decades. Drawing on hundreds of hours of interviews, as well as newly discovered archival material, Shaun Walker brings this history to life in a page-turning tour de force that goes to the heart of what became the most ambitious espionage programme in history. As Moscow continues to infiltrate illegals across the globe, The Illegals shines new light on the long arc of the Soviet experiment and its messy aftermath – and on how that hidden history shaped Russia and the West.