A bestselling fantasy adventure about two teens from two very different worlds, who must work together to save the universe. The companion novel to the bestselling Deep Secret.

Arianrhod Hyde's world (or Roddy, as she prefers to be called) is very much the world of magic, pageantry and ritual. Presiding over all, the most important person is the Merlin, who is entrusted with the magical health of the Isles of Blest.

Nick Mallory's world is much more familiar - at least, it starts off being our own. But Nick's not the ordinary 15 year old he seems, as he slips sideways into something he thinks is a dream - but in fact is another world entirely. Now, Nick's been on other worlds before (although never alone) but he's a confident type. Maybe a bit too confident...

In Roddy's world, the current Merlin expires and a new one takes his place. Yet something is wrong - the rituals have been upset and nothing is going the way it should. Roddy needs help, and Nick might be the one to do it - even if he can't use magic...

Their stories unfold, side-by-side, and the Merlin Conspiracy thickens - two stories combining until the mystery is finally revealed.

Compelling, howlingly funny in places, mind-boggling - this story will wow Diana Wynne Jones fans all around the world (and probably in other universes too).