Mo and Resa are captured by the Adderhead's men along with many other strolling players in the cave, sold out by one of their own. Meggie joins Dustfinger and Farid in searching for her parents and the strolling players. Along with the Black Prince, the leader of the Motley Folk, they launch a successful rescue mission, but Mo is unable to escape because of his wound and Resa stays behind with him. In the meantime, Cosimo's double is ruthlessly killed in a battle along with most of Ombra's men. Meggie goes willingly into the Adderhead's Castle of Night and, fulfilling a prophecy she and Fenoglio dreamed up and "read" into reality, offers him a bargain: Mo, a great bookbinder, rather than the robber they believe him to be, will bind the Adderhead a book of immortality if he lets Meggie, Resa, Mo, and the rest go free. What they neglect to tell the Prince of Argenta is that if three words are written in the book ("Heart", "Spell", and "Death", referencing the titles of the books), the person who signed his name in the book to gain immortality will die instantly. In disbelief, his lieutenant Firefox, is chosen to test it. Firefox is made immortal, surviving a fatal stabbing without suffering any consequences but Taddeo, the Adderhead's librarian, kills him by writing the three words in the book. Satisfied that the book works, the words are erased and replaced by the Adderhead's name, consequently making the Adderhead invincible. Mo picks up Firefox's sword as they leave and claims it as his own, feeling a strange coldness within him; he believes his anger and sadness at the events thus far are changing him into a different person.