The study of Marxism in Britain throws light on what many historians have referred to as “the enemy within’. In this book, David Burke looks at the activities of Russian political emigres in Britain, and in particular the role of one family: the Rothsteins. He looks at the contributions of Theodore and Andrew Rothstein to British Marxism and the response of the intelligence services to what they regarded as a serious threat to security. With access to recently released documents, this book analyses the activities of early-twentieth century British Marxists and brings to life the story of a remarkable family.