In this immersive novel set in 1840s Britain and France, questions of identity probe at the essence of what it means to be human. A wet nurse goes by an assumed name but longs to know the identity of her father. A quarryman furtively extricates a remarkable fossil from an island off the Northumberland coast and smuggles it abroad to Paris. A sensational best-selling book triggers widespread argument and speculation-but its author's name is a secret. Another book, roundly ignored, sets forth the principle that will become the centrepiece of Charles Darwin's Origin of Species. All these threads-some historical, others fictional-converge and illuminate one another in unexpected ways in the climactic revelations of this brilliant story.