On a dark and stormy night in 1816, a teenage girl sat down and invented science fiction. Mary Shelley was no more than 18 years old when she wrote Frankenstein. From the moment of its publication 200 years ago, readers have been wondering, as Mary put it, "How I, then a young girl, came to think of, and to dilate upon, so very hideous an idea?" Outcasts takes readers behind the scenes, to reveal the surprisingly contemporary thoughts and feelings of Mary, an unmarried mother and the lover of radical poet Percy Shelley, their friend Lord Byron, and the other guests at the "most famous literary party in history". What led the daughter of two of the most radical philosophers in England to turn her hand to horror?