The idea of undercover Russian spies and deep cover ‘sleeper agents’ has been a source of much intrigue and speculation ever since the height of the Cold War, inspiring countless works of fiction and continuing to maintain a prominent place in our understanding of espionage. But while TV programs such as long-running FX drama The Americans toyed with the idea of foreign spies hiding in plain sight in the heart of suburbia, in reality the exact same thing was playing out in real-time right under people’s noses. Recently declassified FBI files have now revealed the existence of a vast network...