A hit and run driver puts Cosmo's wife Sophia in a coma. Her mother Sybelle, and her two aunts, Nona and Moira, stand vigil in the hospital while Cosmo, with his companions Nat, Snout and Cat make haste to Castle Perilous to rescue Sophia's Ka from the oily hands of Pluto, the sovereign of the Underworld. En route they meet Lord Elwin, who agrees to guide them across the Forbidden Lands if they help him rescue the Witch-King. The Witch-King's exile has damaged the World-Cloth and made worse an ancient curse that affects Elwin's family. When the fellowship reaches the End of the World, they split into two parties; Elwin and Snout (the last wood elf) go over the wall to search for the Witch-King, while Cosmo, Nat and Cat hurry to find Sophia. Pluto has received word that Cosmo is on his way and he sends two furies, Sturm and Drang to prevent Sophia's husband from reaching the castle and also accelerates the preparation for their wedding. Once Sophia is married to Pluto she will not be able to leave the castle, her physical body will wither and she will be trapped in Hell forever. Sophia finds support from two unlikely sources; a talking mouse and Ixion, a poor man seemingly destined to labour forever, turning a wheel in the basement of the castle. Cosmo, Nat, Cat, Lord Elwin, Snout and the Witch-King arrive at the castle just in time to see Sophia wed Pluto. Through a series of adventures and misadventures Cosmo manages to free Sophia and they flee back to the mysterious Seminary of all Saints where the gateway back to their land and time, exists. In the end Pluto exacts a terrible revenge which only the Redemption of the Witch-King can resolve.