When you're with Geronimo Stilton, it's always a fabumouse adventure Hercule and Geronimo investigate a strange new case. There is a garbage thief in New Mouse City. They aren't stealing just any trash, it's all organic waste. They enlist the help of the head of the Recycling Center to help. In the end they find the thief is a colleague of Floras who has built a machine that turns organic waste into an energy source.