Johnny Dixon, Fergie and Professor Childermass comply with a strange will left by the Professor's brother, which requires them to spend the summer at a desolate estate where they encounter a madman bent on destroying the world.
Jack and his younger sister take a trip in their tree house back to ancient Egypt, where they help a queen's mummy continue her voyage to the Next Life.
The riddles that a pioneer family share explain the origin of such things in their lives as their log cabin, johnnycakes, the broom, a cloak, candles, and more.