Deep Secret

Magids look after all worlds, steer them toward magic, and keep history happening. But Rupert Venables' mentor has just died, and as the junior magid on Earth he must find a replacement while also locating the lost heir of a collapsing empire, worlds away. Rupert interweaves the fate lines to bring the candidates together at a sci-fi/fantasy convention, and havoc ensues as they converge on a very strange hotel where everything is linked, the walls keep moving, people are trying to kill him, and nothing is as it seems.

A fantasy adventure about saving the universe one world at a time from Diana Wynne Jones. A magical, epic story.