"When the mutilated bodies of prostitutes start turning up again, Hammersmith enlists the help of a criminal network to stop Saucy Jack, his methods carrying him further and further from the ideals of the Yard, so far in fact that he may never be able to find his way back.
Of course, the Ripper s been playing a game with him with Walter Day, as well. He is pushing both of them to their limits, and what happens when they get there . . . no one
can tell."(Murder Squad 4)

This is the fourth installmen in a series by Alex Grecian.
The first book   The Yard was followed by The Black Country and The Devil's Workshop.

All of them set in Victorian London.