In the summer of 1993, Thomas Harding travelled to Germany with his grandmother to visit a house by a lake. It had been a holiday home for her family, that she had been forced to leave as the Nazis swept to power. As he began to piece together the lives of the five families who had lived, he realised that this house had witnessed violence, betrayals and murders, had withstood the trauma of a world war, and the dividing of a nation.