A strange boy and dog remind Will Stanton that he is an immortal, whose quest is to find the golden harp which will rouse others from a long slumber in the Welsh hills so they may prepare for the ultimate battle of Light versus Dark. With the final battle between the Light and the Dark soon approaching, Will sets out on a quest to call for aid. Hidden within the Welsh hills is a magical harp that he must use to wake the Sleepers--six noble riders...

Jane's invitation to witness the making of the Greenwitch begins a series of sinister events in which she and her two brothers help the Old Ones recover the grail stolen by the Dark. The priceless golden grail that Simon, Jane, and Barney Drew worked so hard to recover has been stolen by forces of evil. Great-Uncle Merry takes the siblings back to Trewissick in Cornwall, where he expects the Dark has hidden the grail.

In this conclusion of a tale begun in "Over Sea, Under Stone," Will Stanton, the Welsh boy Bran, and the Drew Children try to locate the crystal sword that alone can vanquish the strong forces of the Dark. The last great battle between the Light and the Dark has arrived, engulfing Will Stanton; his ageless master, Merriman; the three heroic Drew children; and Bran, the Welsh boy whose destiny is tied to the Light