The Battle for the Castle — Elizabeth Winthrop

As William turns twelve, he wonders if Jason is still his best friend. In the past year Jason has grown a foot taller while William is still a shrimp. When Jason challenges William to "jump the trains," William is terrified. How else can he prove himself to Jason?

William has the chance when his former housekeeper sends him a magic token that once again takes him back to Sir Simon's castle in the Middle Ages, this time with Jason. There they face a dangerous army of rats and their gigantic leader.

Once William was a hero in the castle. Now it's up to him to destroy the rats and save the kingdom in the final battle for the castle.