When eight-year-old Jack and his seven-year-old sister, Annie, join a group of nineteenth-century explorers aboard the H.M.S. Challenger, they learn about the ocean, solve the mystery of its fabled sea monster, and gain compassion for their fellow creatures.

When Jack and Annie travel back to the Kansas prairie in search of "something to learn," they gain an understanding of how hard life was for pioneers and they experience the terror of a tornado.

While on a mission to prove to Merlin that they can use magic wisely, Jack and Annie travel to seventeenth-century Venice, Italy, to save the city from disaster.

On Christmas Eve, Jack and Annie's tree house transports them to King Arthur's castle at Camelot.

Their magic tree house takes Jack and Annie to the Arctic, where a polar bear leads them onto very thin ice.

The magic treehouse takes Jack and Annie back two thousand years to ancient China, where they must find the original copy of an old legend before the imperial library is burned down by an evil dragon.

The magic tree house carries Jack and Annie to New York City in 1938 on a mission to rescue the last unicorn.

Jack and Annie travel in their magic tree house to the land of the mystical selkies to seek a magical sword for Merlin.

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.

Having used their magic tree house to travel to India, where they must get a gift to help free the dog Teddy from a spell, Jack and Annie have adventures involving a tiger and other endangered jungle animals.