After learning the dark secrets hidden in Mr. Dowling's twisted mind, B is on the run. She escapes the clown's clutches and weaves her way through London's abandoned Underground, only to find that Mr. Dowling has laid siege to the Angels' base in County Hall. And when B learns of the history between Mr. Dowling and someone she trusted, she realizes that she can't rely on anyone—B, and B alone, is the only one who can save humanity.