While watching bats return home, Hamish notices the cave is very dark and asks ‘How do bats see in the dark?’ Brewster takes the gang into the cave where they meet Finbar Bat. He shows them how he uses his ears to listen to echoes and move around.
Brewster and the gang meet Cod Wriggles and ask ‘why is the ocean salty?’ They take a dive into the ocean and use their imaginations to come up with different scenarios before Cod explains that rivers and streams carry salt into the sea from the land.
Brewster, Maggie, and the twins wonder ‘Why do our heads hurt after we drink cold stuff too fast?’ They meet Thinky Brain. He explains that ice makes the mouth cold and when the brain tries to warm things up fast it gives you a headache feeling.
Helvetica notices that both the sun and moon are in the sky at the same time and she asks, ‘Why do we sometimes see the moon when the sun is out?’ The curious friends head into space where they meet Sonny Sun and Mr Moon who explain the reason to them.