Summer of the Sea Serpent — Mary Pope Osborne

In a land lost in mist, in a time before time, there is a powerful Sword of Light. Now Merlin the Magician needs that sword for the good of all Camelot. But who can go on this dangerous mission? Merlin turns again to Jack and Annie - two modern kids with a lot of experience with history, mystery, and magic - for help. And again, Jack and Annie take up the challenge! With only a rhyme to lead them, they set out on another journey filled with fabulous creatures, mysterious riddles, and more than a few surprises!