In the 33rd century humanity is scattered among the planets of the Solar System. Millions of lives depend on the revolutionary physics of Arthur Holywelkin; millions of hearts are moved by the music created by the strange, eerie instrument he built in the last years of his life: the Orchestra. Johannes Wright is the Ninth - and youngest - Master of the Orchestra. But as he sets out on his first Grand Tour of the Solar System, unseen foes are at his heel, ready to reveal all but the meaning of their enmity. In confronting them, Wright must redefine the Universe - for himself and all humanity.