As they are lowered to their supposed execution, Xaxis reveals his plan: he has had a tunnel dug into the sewers, where Magda and Xanth will be pursued by the Rock Demons, who will devour the Librarians. Xanth and Magda manage to stay ahead of the beasts and meet Venvax in the library, bidding him farewell when they realise he will not leave. As the goblin and shryke armies enter the sewers to kill the librarians, Venvax sacrifices his life to let Xanth and Magda escape the goblins. The Shrykes soon engage Tytugg's forces in battle, causing huge carnage. However, the Rock Demons then arrive and proceed to slaughter both sides – any who survive are wiped out in the flood. On board the barges, Rook and Cowlquape realise the purpose of Vox's baby; Vox did not predict the maelstrom, for the sphere of phraxdust will be volatile enough to trigger such an event if it is fired into the sky (a previous attempt caused Rook to crash the Stormhornet). They also realise that, with his escape now assured, there is nothing to stop Vox triggering the storm at any hour he pleases. Rook desperately swims back to shore and climbs up the Palace of Statues to stop the maelstrom. He arrives in time to see the butler Speegspeel move to set off the storm an hour before Vox's 'prediction'. Rook fights and kills Speegspeel, but then releases the storm himself by unintentionally mixing his sweat with the phraxdust. The storm destroys Undertown and the Ghosts of Screetown evacuate all the inhabitants. As the storm reaches its peak, the Guardians of Night attempt to harness the lightning to cure the Sanctaphrax rock of Stone Sickness. However, Mollus Leddix discovers Xanth's theft of the deadbolt too late, and is unable to keep Midnight's Spike aloft. Orbix Xaxis throws Leddix to his death, and insanely attempts to act as a human conductor in the place of the spike. The lightning does indeed strike, but only obliterates the Tower of Night. Rook rejoins with the Librarians, and admits he set off the Storm, which could have been prevented. However, the Librarians forgive him, eager as they are to leave the sewers, and knowing that if Rook had not intervened, the storm would certainly have been triggered anyway. Finally Vox's bower appears. Sensing his thoughts being probed, Rook attacks it to find that the