There's a green comet in the sky and things are getting strange. Every day, fantasy and reality are getting harder to tell apart. Witches in bottles, warmongering cabbages from the planet Pluto, and disguised goblins on the loose in London town.

Jack Ember is caught between two very unreliable mentors. Gus might be a wizard or a madman - or both. The Kind Gentleman is the sort of faerie godfather who'll grant you three wishes you can't refuse. Both of them have plans for Jack, who's spent his life dreaming of adventure and now is about to get the adventure of a lifetime.