Like Shakespeare's Richard III, arch-villain Mordred has now been fictionally upgraded to Mr. Nice Guy--with Stewart continuing her inventive, entertaining re-do of the Arthurian legend. Stewart gives all those traditional magic didos short shrift: Mordred's mother Morgause, ""the witch of Orkney,"" doesn't raise any shades here--but she raises hell aplenty. Having brought Mordred to her palace, away from his fisher-folk foster-parents, Queen Morgause tells him he's really the by-blow of her dead spouse King Lot. (Mother unknown.) And Arthur, she says, hopes to do Mordred in because Merlin has predicted that Mordred will be Arthur's ""doom."" So child Mordred, earnest and quite thrilled, is raised in Morgause's household, along with his four half-brothers. He grieves when he discovers his foster-parents burned to death (guess who arranged this); he's considerably disconcerted when Morgause, leading him into her magic cave, shows a peculiar incestuous interest. And at last Mordred meets King Arthur, who sets him straight: Mordred is Arthur's son by his half-sister Morgause! (On Arthur's part, an innocent mistake.) Complications ensue--as Mordred tries to stay loyal to Arthur. After swordplay in Guinevere's bedroom, where his half-brother knights (who have ""the minds of wild cattle"") attack suspected lover Bedwys (Lancelot), Mordred escapes to farm-country. But he returns at last, King Arthur naming him official heir and deputy-king. To be sure, Mordred's decent ambition and abilities lead him to over-extend a bit here--but he's a good fellow throughout. And the closing battle/death is caused by mishaps and such--with Arthur spirited off to the vale of Avalon by non-magical courtiers. . . who do their Red Cross medical bit in a barge. Despite some mediaspeak (""fact-finding mission"") now and again: a fine Stewart mix of clever myth-revamping and fast, chatty action.