Dark Stars - C.S. Quinn

The Great Fire has reduced London to smouldering embers. From the ashes, thief taker Charlie Tuesday is drawn to investigate a string of strange murders. Mutilated corpses are washing up at Deptford, each marked with a dire astrological prediction. But only London's best crime-solver realises the killer's deadly offerings will soon unleash a devastating force on England.

With the help of Lily Boswell, a gypsy street-girl with a knife and a grudge, Charlie must find the killer and put a stop to the murders. And by doing so, the Thief Taker will find the man whose terrible destiny is entwined with his, their fates written in the dark stars

This is the third book in the Thief Taker Series but can be enjoyed as a stand-alone story.