Strange occurrences happen in the museum during the Spiez' field trip. Prehistoric creatures come alive. The Spiez investigate when they discover that an anthropologist acting like a caveman plans to return the world into the dinosaur age. The Spiez get trapped in an erupting volcano, but escape. They hurry to their hometown to finish destroying the dinosaurs and defeating the anthropologist just in time to get home before their parents arrive. In the B-story, Megan thinks that their parents are having a baby girl and is jazzed that she will not be the only girl.
