Misho and Robin are underground - they are digging a hole searching for dinosaur bones. To be more specific, they're looking for T-Rex. Suddenly, the ground gives in and they fall deeper. Soon they make friends with Mole and explain to him what they had been doing. Mole takes them for a tour of the underground in his little train and shows them bats, ants and finally - a big surprise - the room full of dinosaur bones!