Eight-year-old Joe is about to become a big brother. His mother is in labor at the hospital when he looks outside and sees a little boy hanging upside down in an apple tree. It's Mika, who has just fallen out of a spaceship. Mika is from Eljo, where children hatch out of eggs and life in general is quite different from what Joe knows. Mika and Joe become instant friends and spend the day discussing everything from dinosaurs and gravity to the origins of life on earth. The next morning, Mika is gone. But Joe has a new appreciation for the wonders of the universe -- and a baby brother!