This is a biography of one of the most influential families in the history of ideas. William Godwin's treatise on liberalism, "Political Justice", brought the ideas of the French Revolution to Britain. "A Vindication of the Rights of Women" by his wife, Mary Wollstonecraft, marked the start of the modern women's movement. At a time when Godwin's early achievements had been largely pushed aside, the poet Shelley ran off with his daughter, Mary Godwin, who wrote "Frankenstein". The book is based on an exploration of the vast family archives. Amongst other discoveries, the author has decoded a secret diary recording Godwin's sexual relationship with his wife. In the case of a family who in their writings advocated greater sexual freedom, this information has more than a personal interest.