Humans create robots, aka Chumballs, to restore a damaged Earth. The reason for these robots is due to the fact that a catastrophe happened on Earth, making it unlivable and forcing humans to live underground. After the Chumballs have completed their task, they have to send a signal to the humans. But something is wrong. There is no signal received. So three kids and a robot go on a journey aboveground to search for the Chumballs.