Dave is thrilled when he wins an electronic home help device called Barry - finally, his family can boss something around other than him, but it is not long before Barry is overwhelmed by the Spuds' demands. Fighting back, Barry takes over Grimsby Heights and heads off to the sea for some well-earned peace and quiet.

Dave and his friend Zombie Katie are working on a school project together about endangered animals, so George takes them on an expedition to the local park to see what they can find. There they discover the much-fabled Beast of Grimsby - and Dave must decide between a gold star at school and the future of the beast.