The Awful Secret (Crowner John Mysteries)

Gilbert de Rideford is a Knight of the Temple of Solomon, and an old acquaintance from Crowner John's crusading days. He claims to have come into possession of a secret that could shake Christendom to its foundations—and he desperately needs John's help to escape from the secretive order of warrior monks. Suddenly swept into a world of religious intrigue and dangerous politics, Crowner John finds himself undertaking a life-threatening mission to the Island of Lundy—inhabited solely by notorious pirates—until finally the awful secret itself is revealed.