Mr Campion's Coven

East coast of England, 1971. Albert Campion is invited to assist Harvard student Mason Clay on a research trip to Wicken-juxta-Mare. But Wicken is already firmly on Campion's radar thanks to Dame Jocasta Upcott's beached luxury yacht, its captain very stuck - and very dead - in the mudbank. Was it a bizarre accident or something more sinister?