Witch Hunt by Stephen Leather

Supernatural detective Jack Nightingale has always dealt with unusual - and dangerous - cases. So when a serial killer starts killing victims using Witchfinder methods of execution, Nightingale is asked to help. As the body count mounts, Nightingale realises that the killer is on a mission of revenge for acts committed four hundred years ago. And he and his assistant Jenny McLean are both on the killer's hit list.

Jack Nightingale appears in the full-length novels Nightfall, Midnight, Nightmare, Nightshade, Lastnight, San Francisco Night, New York Night, Tennessee Night and New Orleans Night, and numerous short stories. The Nightingale timeline is complex; Witch Hunt is set between Nightshade and Lastnight, back when Jack Nightingale was in London working with his long-suffering assistant Jenny McLean.