Two young boys sneak aboard a spaceship and find themselves whisked away to the mysterious planet Terra. There, they encounter Gamera's old foe Gyaos and two female aliens with a taste for human brains. Gamera must save the children and battle the new monster Guiron, whose entire body is a deadly living weapon.

Two children get into a flying saucer and end up on the other side of the sun where they dream of donuts and milk and a hero turtle. The women there want to eat their brains.