The Alden children find a hidden cave in the old woodshed, resolve the problems that have plagued the Alden farm and patch up the misunderstanding between Aunt Jane and Andy Bean.

Tom and Jamie discover a secret entrance to a prehistoric world filled with dinosaurs, including a friendly plant-eating Wannanosaurus and a fierce Tyrannosaurus Rex.

As Tom and Jamie explore the prehistoric world they found through a secret cave, they come across a young ankylosaurus stuck in the mud and try to find a way to save it.

Bill Nye looks at caves and the life forms found inside them.