At an end-of-London-season soiree, the young Hungarian scholar-dilettante Janos Batky is introduced to the Earl of Gwynedd, a reclusive eccentric who is the subject of strange rumors. Invited to the family seat--Pendragon Castle in North Wales--Batky receives a mysterious phone call warning him not to go; but he does and finds himself in a bizarre world of mysticism, romance, animal experimentation, and planned murder. His quest to solve the central mystery takes him down strange byways--old libraries and warehouse cellars, Welsh mountains, and underground tombs.