The haunting of Alaizabel Cray - Chris Wooding

Perfect for fans of Neil Gaiman and Sherlock Holmes, this award-winning
gothic thriller returns.
London has survived war and plague only to face a new horror - the
Wych Kin. All kinds of demons lurk in the labyrinth of the Old
Quarter, and it is the task of wych-hunters such as Thaniel Fox to
keep them at bay. Then one night he rescues a young woman who has
lost her memory: the beautiful and vulnerable Alaizabel Cray.
But Alaizabel is nursing a dark secret, one that even she does not
understand, a secret that could unleash the most terrible evil
of all - and bring destruction to the world.