...that's the cryptic route followed in this story which starts as a typical Juvenile mystery/adventure but then turns out to be a morality tale with a struggle between forces of good and evil. Simon, Jane and Barney Drew go with their parents on a vacation to an old house in Cornwall Which their Great-Uncle rented for the occasion. Great-Uncle Merry is a scholar specializing in Arthurian history and legend, a mysterious person who seems larger than life. The children decide to go on a quest and immediately locate a hidden chamber and an aged manuscript. The manuscript turns out to be a description of the hiding of Arthur's grail and of the key to its understanding which were supposed to usher in the Coming of the new Pendragon ("And that day shall see a new Logres, with evil cast out; when the old world shall appear no more than a dream."). Only the children are able to carry on the Search. Great-Uncle Merry seems to know all the answers, but he can only watch, advise a little, and protect them from the forces of evil represented by a personage mas-querading as the vicar and a fashionable young couple yachting in the area. The story, which starts slowly, becomes more compelling as the supernatural starts to take over, although the mystic powers never reach the terrifying proportions they should have, and the ending, necessarily ambiguous, seems uncomfortably contrived. The theme of good and evil in violent opposition is always a forceful one, but beyond this book's capacity.