In 1827 Harriet Smithson, a beautiful and talented young Irish actress, makes an unusual decision. Determined to avoid the traditional route to stardom via the manager’s bed, she joins an English company in the bold experiment of taking Shakespeare to Paris. With the ferment of revolution in the air, the new generation is longing for a novel kind of passionate, spontaneous art. And to Harriet’s astonishment, it is embodied in her—*La Belle Irlandaise*. In the midst of this frenzy she finds herself pursued by a strange, intense young composer named Hector Berlioz. So begins a painful and profound love affair. She is his muse, his *idée fixe*, his obsession; and Berlioz’s *Symphonie Fantastique*, directly inspired by Harriet, will change music forever. *Symphony* is an audacious, brilliant, and haunting novel, set against a background of nineteenth-century theatre, Romantic art, music, and revolutionary Europe. But at its heart lies the story of two lives transfigured and destroyed by genius, inspiration, and madness.