Look to the Lady (1)

Campion learns that a mediaeval relic called the Gyrth Chalice, which for hundreds of years has been in the care of the Gyrth family at the village of Sanctuary, is threatened by an international gang of art thieves. For the Gyrths the stakes are high - if they lose the Chalice, their country estate will revert to the Crown. Campion travels to Sanctuary with Val Gyrth, and almost at once Val's aunt Lady Diana is found dead in the middle of a wood, apparently frightened to death... it seems the gang is already on the job.