If they fail, Camelot will be forgotten forever. Fans of the beloved, highly readable series by Mary Pope Osborne will rise to the challenge of this longer, more complex companion to her other titles, which include Earthquake in the Early Morning and Twister on Tuesday. As in every story in the sequence, Jack and Annie bravely plunge into their quest, learning about a culture and time very far removed from their own, and prove once again that children can make a difference.