This is the story of what happens one quiet weekend in Ashton, when Henry unexpectedly finds himself joining the Ashton Adventurers to compete for the Brainbox of the Year Cup, when Mum and Dad try to slip away for a night without the kids and when Great Aunt Greta has teenager to stay. It's the story of how Henry learns to work as a team, battling alongside Moody Margaret, Beefy Bert and Anxious Andrew against his nemesis, Stuck Up Steve, and the Brick House Boys. It's the story of the secret life of a cat (and a hamster) as we discover what Fluffy and Fang get up to when they are left to their own devices in the Henry household. It's a story of bravery and heroism, of greed and sacrifice, of failure and ambition. But above all it's the story of the love of a perfect little brother for his Horrid big brother.