"In a sleepy Japanese village, five children elect to take a week of summer school away from their families at the local school house. On the first day they find and nurse an injured dog, who reveals himself to be a canine-like alien named Pochi. As thanks for saving him, Pochi takes the kids to visit a secret alien metropolis on the dark side of the moon. But when his report on the poachers he was investigating causes all space travel to Earth halted, the children have to find another way home. As this is happening the poachers shadow their group in pursuit of a rare plant that may have survived on Earth and is rumoured to carry a secret power."