No one knows why Harry is wearing a necklace. Sidney thinks they're for girls. But when Harry opens the necklace cover and reveals a mini-microscope the whole class is intrigued. Everyone wants to try it, so Harry promises to show them all a kingdom of mushrooms at recess. But he doesn't tell them that to see it they'll need to go outside the fence -- and that means breaking a school rule. Will everyone follow him? What if they get caught? Has Harry gone too far this time?