An alternative-history classic nominated for the Hugo, Nebula, and World Fantasy Awards!Young Mary Godwin has run away with the married poet Percy Bysshe Shelley, but a chance encounter places them in the path of Lord Byron, the Hero of Waterloo. Byron wants Mary, and is willing to use Mary's young, reckless sister Claire as a pawn in his heartless schemes. Exactly how heartless, and how audacious is only revealed on a storm-tossed lake in Switzerland, a tragic encounter that produces not only an alternate history, but an alternate literary monster, a new Frankenstein for a new world...