Why are extraordinary creatures disappearing from the Banana Sanctuary for Amazing Animals? When explorer Billy Banana mysteriously vanishes while on a mission to rescue the world's deadliest – and smelliest – Amazonian frog, his son Arthur is left home alone. Can Arthur save their beloved sanctuary from the clutches of Aunt Hernia and her gang of terrifying underworld villains?

With the help of cousin Rubella, the pair of young eco-warriors desperately try to foil Hernia's dastardly plot to turn the sanctuary into flats. Easier said than done when your master plan involves a zombie sloth that only wants to eat brains, a penguin with an attitude problem and a miniature gorilla who refuses to be squeezed into a pair of pyjamas for an important meeting!