Witch's Sabbath — J.M. Gregson

Chief Inspector Percy Peach, Detective Sergeant Lucy Blake and the team, hindered as usual by the direction of Chief Superintendent Thomas Bulstrode Tucker, have one of their most puzzling and compelling mysteries to solve.
In an area famous for the Lancashire Witches four centuries earlier, it seems that witchcraft still flourishes. When a body is discovered in a derelict farmhouse, it is partly mummified, a pathetic ruin. Although an identity is quickly established, that is only the first of many problems. No one reported this young woman's disappearance when she went missing four months earlier. Most of those who were closest to her, from her former employer to her newly-acquired boyfriend, had reasons to keep quiet. Her flatmate, a woman of her own age, seems to have been very sure that Annie Clark was never going to return. And it appears she was a member of a modern coven, containing both male and female members...