In this book, which is the first in the series, readers will get to meet a new Geronimo Stilton in a world parallel to that of Earth: Geronimo Stiltonix. This little space mouse is busy flying the spaceship Mouse Star 1 through the cosmos. During his special journey, he discovers many new planets and meets new aliens. But suddenly, the poor mouse finds that his spaceship has got into a soup and that unless the batteries of its engine are replaced, he could well explode into bits with the ship.