Through a misunderstanding, Junie B. thinks that her new baby brother is really a baby monkey, and her report of this news creates excitement and trouble in her kindergarten class.
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.
Marvin is pleased when his teacher asks him to take care of her dog while she's away, but he soon finds that there's more pressure involved than he likes.
The Magic Tree House takes Jack and Annie to a moon base in the future where they continue to search for the fourth thing they need to free their friend Morgan from the magician's spell.
The magic tree house transports Jack and Annie on a mission to the Ice Age where they encounter Cro-Magnons, cave bears, sabertooth tigers, and woolly mammoths.