Xax has taken a convoy of Warriors out on a hunt - and has a fantastic piece of luck when Will and the band stumble right into his path. They are chased by the horsemen across an open plain, with nowhere to hide in sight. Capture seems inevitable, when out of the mists ahead of them their looms a dark and forbidding castle - which certainly wasn’t there before ...

With no time to think, the band rolls under the vast gate of the castle just as it clangs shut. Safe from Xax, our heroes discover a new dilemma now faces them.

This is the Castle of Doubt, where every good thing has its evil counterpart, and nothing is what it seems. There are two exits to the Castle: one leads to safety - the other to destruction.

The only inhabitants of the Castle seem to be the Master himself, a benign but infuriating old man who speaks in philosophical riddles, and his two servants, the identical twins Pinto and Tamlin. Tamlin can speak only truth; Pinto can speak only lies - but how is anyone ever to tell them apart?

And learning to ask the right questions is the crucial lesson the Castle of Doubt exists to teach. Discovering how to trust your own instincts becomes imperative for Will when Drogo and Vara fall into deadly danger, and he must somehow work out how to escape the Castle in order to save them.

Will realises that a true leader must use his wits as well as his courage in order to be worthy of his responsibilities.

The people of the nearby village rally around the rebels to protect them from Xax, who has set up an encampment and laid seige to the Castle.

The band escapes to find Kalem once more: Kalem, who has spent this adventure masquerading as ... the Master of Doubt.