The precarious equilibrium among the four Londons has reached its breaking point. Once brimming with the red vivacity of magic, darkness casts a shadow over the Maresh Empire, leaving a space for another London to rise. Kell begins to waver under the pressure of competing loyalties. Meanwhile, an ancient enemy returns to claim a crown and a fallen hero is desperate to save a decaying world...

Kell is one of the last Travelers -- magicians with a rare, coveted ability to travel between parallel universes--as such, he can choose where he lands. There's Grey London, dirty and boring, without any magic, ruled by a mad King George. Then there's Red London, where life and magic are revered, and the Maresh Dynasty presides over a flourishing empire. White London, ruled by whoever has murdered their way to the throne -- a place where people fight...