When Marshall's old trainers disappear, he suspects his sneaky sister. But then other stuff starts to vanish - right in front of his eyes! His homework, the food from his plate, and even the gum stuck to his desk!
The crazy thief seems to be some sort of invisible creature. Marshall and Simon are sure it's the strange new kid at school. But where do his amazing powers come from? Where is Marshall's stuff? Or could the right question be - "when" is it?
