Presented in two versions for younger and older children, this tale is of two teenagers in a European castle more than 200 years ago. The youngsters are called upon to help against an attack from a large number of frightening marauders who appear to be huge black blocks. The king appoints Gertrude to help with the preparations for battle, and then sends her brother, William, to seek help from neighbors. While alone in the world for the first time, William learns about both beautiful and dangerous villagers before boldly enlisting the aid of giants. William and the giants arrive almost too late, as the destruction of the castle by the terrifying black blocks has already begun. Yet, the giants are able to defeat the black blocks to save the day, and the king makes William a knight. In a surprising end, the identities of the black blocks and the giants are revealed.