Andy and Terry's incredible, ever-expanding treehouse has thirteen new storeys, including a watermelon-smashing level, a wave machine, a life-size snakes and ladders game (with real ladders and real snakes!), a rocket-powered carrot launcher, a Ninja Snail Training Academy and a high-tech detective agency with all the latest high-tech detective technology. Which is lucky, because they have a big mystery to solve - Where is Mr Big Nose?