The next book in the Todhunter series. So to speak. Tod herself does not appear for quite a bit. Indeed, in the first portion, the returning characters are the evil wizard, and Spit Fyre.
But the wizard Oraton-Morr takes the last Orm egg out into the desert, takes a baby hostage to ensure its safety, and goes off to wait for its hatching, so he can make it imprint on him. But the boy set to watch the egg at one point steals the turtle of the sister of the kidnapped baby, and that sister, Kaznim, steals something from him and sets out to find her turtle. Alas for her, this puts her through an unstable Way, where she stumbles on Sam Heap and Marwick, who tell her there's no easy way back. They take her with them to the Castle -- it becomes progressively clearer than Sam is desperately injured -- and arrive back, even managing to reach the people on the other side of a Seal and get out.
Despite the pother over Sam, they manage to notice that Kaznim has things related to the Orm egg, which they know could be extremely dangerous if Oraton-Morr succeeds.
It involves a sled race, a witch who's decided to freelance, the history of a healer at the Wizard's Tower, Tod's best friends being taken for Snow Sprites, a malicious ghost, a charm used out of place, a vicious queen, a tiger, and much more.