After hurting his leg playing football, Conor has to use a crutch and isn’t able to walk very far. This gets the children thinking about how different animals get around. They go on a trip with Mr O’Dear to the nearby Periwinkle Lagoon, to see the fish and birds that live there. When they arrive they bump into Gull McGill, a fast-talking seagull who joins them as they follow the trails different animals have left behind and track a mysterious new species.