The Glass Devil

Detective Inspector Irene Huss of the Goteborg crime force and her boss drive out to a remote cottage in snowbound southern Sweden as a favor to his cousin, a school principal. They have been asked to look into a teacher's absence from school.
In the cottage, they find the body of a man, killed by two shotgun blasts. Jacob Schyttelius's absence is explained: he has been murdered.
When they go to the rectory to break the news to his elderly parents, Pastor Sten Schyttelius and his wife, they find the couple dead in their beds. Each has been shot between the eyes. On their son's computer screen and on theirs, upsidedown pentagrams have been drawn in blood. Could these murders be the work of a Satanic cult? But there are plenty of suspects in the parish with motives ranging from ambition to greed.
The only surviving member of the family is a daughter living in England. Irene Huss has a hunch that the answer lies with her, but Rebecka is too distraught to be interviewed. Irene refuses to take no for an answer.