A tree house that travels through time? Not possible, says Jack. But he has to admit--when he and his younger sister, Annie, start running into dinosaurs--that they're not in Frog Creek, Pennsylvania, anymore. Eight-year-old Jack and his younger sister Annie find a magic treehouse, which whisks them back to an ancient time zone where they see live dinosaurs.

No girls allowed at the Olympic games! That's the rule when the Magic Tree House whisks Jack and Annie back to ancient Greece. But when Annie tells Jack to go to the games without her, he knows she's up to something. Will Annie find a way to see the games? Or will she get herself - and Jack - into Olympic-size trouble?

When Uncle Al is kidnapped by Dr. Kron-Tox and sent to prehistoric times, Andrew, his cousin Judy, and Thudd the robot try to use Uncle Al's latest invention, the Time-A-Tron, to rescue him, and learn first-hand about the origins of the universe.

Guided by a magic rhyme, Jack and Annie travel to ancient Baghdad on a mission to help the caliph disseminate wisdom to the world.