Hidden far beneath the modern city is London Below, a strange alternate world of swirling colors, magic and gothic danger, populated by misfits who have, quite literally, fallen through the cracks of the workaday world above. The tale begins as Richard Mayhew, a decent but very ordinary man, stumbles across Door, an extraordinary young lady from a London. His single act of kindness immediately costs him his fiance, brings a pair of unthinkably ruthless assassins to his flat, and sends him on a quest that could quickly end with his own demise.