In January 1818, when her novel Frankenstein was published, Mary Shelley was 20 years old and living in a cold, damp house near London with her freethinking and free-loving husband, the poet Percy Bysshe, their two surviving children, William, aged two, and Clara, aged four months, her stepsister and Percy’s admirer Claire and Claire’s baby daughter by Lord Byron. We know how the dark and brilliant novel about the eponymous doctor who manages to create life was prompted by Byron in the summer of 1816, when he suggested, at a gathering on Lake Geneva, that each member of the group write a ghost story.