Welcome to Grey London, dirty and boring, without any magic, with one mad king―George III. Then there is Red London, where life and magic are revered, and White London, a city slowly being drained through a magical war down to its very bones. And once upon a time, there was Black London... but no one speaks of that now. Officially, Kell is one of the last Antari―magicians with a rare, coveted ability to travel between parallel Londons―and acts as an ambassador and messenger between the Londons, in the service of the Maresh Empire. Unofficially, he's also a smuggler, which is a dangerous hobby for him to have―as proved when Kell stumbles into a setup with a forbidden token from Black London. Fleeing into Grey London, Kell runs afoul of Delilah Bard, a cutpurse with lofty aspirations, who first robs him, then saves him from a dangerous enemy, and then forces Kell to spirit her away for a proper adventure. But perilous magic is afoot, and treachery lurks at every turn. To save all of the worlds, they'll first need to stay alive. Prepare to be dazzled by a world of parallel Londons―where magic thrives, starves, or lies forgotten, and where power can destroy just as quickly as it can create.