Mo falls from her father's spaceship as it hovers low over the Earth, and a group of children finds her in the forest. She tells them her father will pick her up after nightfall in a certain forest glade, and the children decide to help her.But their troubles start when none of the grown-ups will believe Mo's story. Mo runs away, the children after her, to spend a bewildering day learning about the funny and sometimes frightening ways of Earth's inhabitants.