Axel trips and falls down a shaft in the volcano. Axel! Where are you? The Professor and Hans finally find Axel. Oh - my head! Don't worry - you're going to be fine. While we were looking for you, we found something amazing. Come and see! The Professor and Hans show Axel their discovery. A sea! And trees! An underground world! Yes! And that's not all... We found the bones of animals that have been extinct for millions of years! This is from a dinosaur! We must cross this underground sea, so Hans is building a raft. This all seems like a dream... Two days later, the raft is ready and they set sail. This sea is too big. We'll never get across it! Nonsense! Of course we'll make it. They sail for many days. Late one afternoon,... Oh no! What's that? It's a..., a... monster! Suddenly, another monster appears... Grrr! Hiss! But, those are dinosaurs, and they're extinct! The monsters fight... Amazing!