Harley Hitch returns for an airborne adventure! The Aviation Parade is coming to Forgetown this summer, and Harley has her sights set on creating a flying machine that will really stand out: a robot hippogriff! And if the creature impresses Cosmo's mum enough, surely Cosmo will be able to keep it as a pet? But Harley wants the flying machine to be a surprise for everyone. She soon finds that keeping secrets leads to tricky explanations and lots of trouble - especially when REAL hippogriffs arrive and cause chaos!