Found: YA book with Jack the Ripper-like killer with carriage

I am trying to recollect the name of a book I read in high school. In the first chapter (I believe), a woman who is a prostitute is killed by a man, nicknamed "Stitchface," who rides a carriage pulled by a black stallion and white mare. I believe that there is also later on in the book a horse demon, aptly called the Night Mare.

The Haunting of Alaizabel Cray ?

Yes, that's it! Thank you.