Look to the Lady by Margery Allingham
Finding himself the victim of a botched kidnapping attempt, Val Gyrth suspects that he might be in a spot of trouble. Unexpected news to him - but not to the mysterious Mr Campion, who reveals that the ancient Chalice entrusted to Val's family is being targeted by a ruthless ring of thieves.
Fleeing London for the supposed safety of Suffolk, Val and Campion come face to face with events of a perilous and puzzling nature - Campion might be accustomed to outwitting criminal minds, but can he foil supernatural forces?