With the sacred key in his possession, only one person stands in the way between the Angel and his ultimate ambition - Door. As the apocalyptic climax looms, everyone faces their own destinies.
Our band of heroes attends another floating market. Door meets an old friend and Richard makes a new one. Old Bailey must make good on his debt. Richard, Door, and Hunter seek Downstreet in an attempt to find their way back to Islington.
Angel Islington is the only person who can tell Door who killed her family and help get Richard back to his old life. But how do they get to him? The Marquis suggests a visit to Earl's Court - but it has a worrying tendency to move around. Meanwhile, Croup and Vandemar alert Door to the fact that there is a traitor in her midst... but who?
Richard Mayhew leads an ordinary life in London when one day a girl named Door falls, injured, across his path. The next thing he knows, his life is gone and he's pulled into the fantastical world of London Below. Pursued by the murderous Messrs. Croup and Vandemar, Door and Richard with the help of Hunter and the Marquis de Carabas, attempt to find the Angel Islington, who knows the secret behind the murder of Door's family, and possibly a way for Richard to go home.