Chapter 2. The Day Horse
Imbri meets a white mundane horse, but he is frightened away. She then meets the horse's master, who convinces her to give him a ride since they're traveling in the same direction. After much confusion on conveying directions, she allows him to put a bridle on her. He then introduces himself; he is the Horseman! Imbri's memory returns, but she has already been captured. The Horseman digs in his spurs and forces her to his camp of Mundane Invaders. They light a fire so she can't dematerialize when night comes. When the guard falls asleep, the handsome day horse sneaks in and puts out the fire (think about it,) letting Imbri escape. He tells her that she can always meet him again at the baobab tree.
Chapter 3. Centycore et Cetera
Imbri meets Chameleon (who is in her stupid/pretty stage) and delivers the message to King Trent. The Nextwave of Mundanians is coming and the Horseman must be connected somehow. Imbri and Chameleon travel to the Good Magician Humfrey to get his advice. The three challenges they face to get in his castle are a Nix, who freezes and thins the water in the moat, a Centycore who tries to eat them, and some Spriggan who try to collapse the building on them.
Chapter 4. Forging the Chain
Humfrey's advice is this: Break the Chain. Imbri and Chameleon return to Castle Roogna to see the "elopement." Dor and Irene were never able to decide on a date for their wedding, so Irene planned to have them wed by the zombie Justice of the Peace in the zombie graveyard. However, everyone knows about it and comes, disguised as zombies by Queen Iris's illusion. Imbri meets Ichabod the mundanian and they have an interesting time at the refreshment table, where the Queen's drinks have been replaced with things like Boot Rear, Injure Jail, and other unsavory refreshments. Chameleon, Ichabod and Imbri find King Trent in the library, but his mind is gone!
Chapter 5. Sphinx and Triton
Dor assumes the crown and assembles a party to spy on the mundanes. Imbri goes to the Baobab tree and convinces the Day horse to help them. He, Imbri, Chameleon, Ichabod, and Grundy travel to the mundanes, running into a sunburnt Sphinx and some Tritons on the way.
Chapter 6. The Next Wave
Imbri, Ichabod, and Grundy spy on the Nextwavers, but get captured. Ichabod identifies them as Punics, and after a talk with their leader, Hasbinbad, they are locked up. Imbri encounters the Horseman again, but he agrees to let them go if she will tell him how she escaped last time. She does, then frees Ichabod and runs for it. However, Ichabod gets shot by an arrow before Imbri can get far enough from the torches to turn immaterial. They rush to the Water Wing where Siren gives them some healing elixir. Then they return to Chameleon and the Day Horse and go back to Castle Roogna.
Chapter 7. The First Battle
Dor's army battles the Mundanes, but when Dor goes mindless like King Trent, they lose.
Chapter 8. The Zombie Master
Jonathan becomes king and uses his zombies to hold back the Mundanes at the Gap Chasm bridge. Chet cuts down the bridge, leaving the Nextwave trapped on the other side. During the night, Imbri and Grundy are talking to Jonathan when suddenly he is ensorcelled right in front of them! They learn that a man was hiding in a tree at the time, and then ran off.
Chapter 9. Good King Humfrey
Humfrey becomes king, even though he knows he will not break the Chain because he will make a disastrous oversight. He informs them that Bink will be the next King, and there will be five more after him. Humfrey tells Imbri what each of his spells is for, then sends some Spy I's and nymphs to spy on and lure the Mundanians, who have defeated the Gap Dragon and crossed the Gap. Imbri and the Day Horse fetch Chameleon and bring her to the isthmus to pick up Bink and Arnolde, who are returning from Mundania. They are almost there when Grundy appears on a magic carpet and tells them that Humfrey has been taken.
Chapter 10. Magic Tricks
Bink is informed of the situation and rides Imbri back to Castle Roogna. They discover that Humfrey bottled his voice when he saw the ensorceller, and pull the cork. The magician's voice says "Horseman!" Bink works up a theory: the Horseman is really a Xanthian, aiding the Mundanes so they and the Xanthians destroy each other, leaving him to take over. The remaining Mundanes arrive and Bink holds them off alone with the great pile of magic spells left by Humfrey. The book of Words of Power works for a while until he loses it. He then battles swords with Hasbinbad until he calls a truce until dawn.
Chapter 11. Centaur Input
Imbri fetches the help of the centaurs from Centaur Isle, and returns to find Hasbinbad dead and Bink injured and ensorcelled. As king, Arnolde Centaur "interprets" the law: it says to queen may rule, but it doesn't say a king must be male. That makes Iris and Irene next in line. They realize that the Horseman ensorcells by creating a line-of-sight between someone's eye and a hypnogourd. Imbri travels into the gourds and finds the kings' spirits--they are comfortable, even if they can't escape. She brings Irene physically into the gourd so she and Dor can finally have a moment together. The centaurs travel to the Mundanes but are ambushed. Goldy Goblin sends a message that she'll help, and Arnolde is ensorcelled.
Chapter 12. King Queen
Queen Iris takes over as King and fights the Mundanes with her illusions; frightening them into running into danger and disguising other dangers as safe places. She is ensorcelled and King Irene takes over. She proclaims Chameleon, who is now in her smart stage, the next King. Chameleon suggests to Irene to pretend to like the Horseman until she's fathomed his secret. Irene grows some defensive plants around the castle while Imbri and Chameleon leave to take out the other Gap bridge. Chameleon secretly names Imbri the next king, and rides the Day Horse back to Castle Roogna. Imbri tells Gorgon, Siren, and Goldy Goblin to go to the castle, then goes into the gourd world to pick up Blythe Brassie. Irene and Chameleon are already there, having been ensorcelled, and the Horseman is trapped inside Castle Roogna by Irene's plants. Chameleon tells Imbri that the Horseman is a were-horse: the Day Horse!
Chapter 13. Breaking the Chain
The rest of the males are sent away for their own protection as Siren lures the Mundanes into the Gorgon's sight, with help form Goldy and Blythe. But they are in sight of the castle and thus are being ensorcelled one by one. The few remaining Mundanes attack the plant-covered castle and Imbri has a startling realization: she's in season! When night falls she flies inside the castle and faces the Horseman, who blinds her with a sunspot. Jordan, one of the castle ghosts, guides her to safety and tells her of a melting spell to melt his magic sword. But the Horseman transforms into the Day Horse and Imbri, since she is in season, is unable to fight him. At last she breaks free, but kills him; now they can't undo the ensorcellment. Imbri takes the brass band he always wore to Blythe, who identifies it as a short circuit. Imbri takes it to the heart of the Void, nulling it, but is unable to escape and dies. Humfrey, now free, uses a spell to keep the half soul Imbri got from Chem from returning to its owner. Imbri is now a Daymare, delivering pleasant daydreams instead of scary nightmares, and finally gets to see a rainbow.