Grail Quest #2: Morgain's Revenge by Laura Anne Gilman

King Arthur's Knights of the Round Table are preparing once again to set out in search of the legendary Holy Grail. This time Morgain le Fay is determined to stop them at any cost, and she knows exactly who is standing in her way. When she kidnaps Ailis, the servant girl whose untrained magical powers grow stronger with every passing day, her vengeance seems to be taking a terrifying turn. Gerard and Newt must work together again to rescue their best friend before it's too late...before Morgain turns Ailis to evil...before Ailis helps Morgain destroy Camelot.