When Richard Mayhew comes to the aid of an injured girl on the streets of London, his mundane life spirals into the depths of the city's dark underworld. His good Samaritan act draws him into 'London Below' - an eerie realm of shadows and forgotten souls. Here, Richard encounters a host of bizarre characters and malevolent entities, finding himself on a perilous quest alongside the noble Lady Door, who seeks to uncover the truth behind her family's assassination. As Richard's reality blurs with this otherworldly labyrinth, he must decide how far he's willing to go to help Door and secure a way back to his own, increasingly distant, life.