Rosie Chesterfield is a young schoolgirl with a bright curiosity for all things science and science fiction. Struggling to concentrate on her homework as her deadlines loom, she is about to make a life-changing discovery from a most unexpected source. You see, human beings are not the only species in the galaxy that enjoy sightseeing! When the Xylon family visit their favorite planet, Earth, in their new cruiser, something unearthly is accidentally left behind!The chase is on! Can the Xylons reclaim their property before it falls into the wrong hands? After all, Rosie wasn't the only one to notice that something alien had just landed...