Ten-year-old Ryan Wolf has a secret: he is the protector of the Eigenoids, a group of creatures tinier than dust particles who live in a box given to Ryan by his grandfather. The Eigenoids use their magic to shrink Ryan down to their size in order to help him learn about the world around him. During a baseball game, Ryan gets a splinter in his finger. After hearing about how his grandfather lost part of a finger due to an infection from a splinter, Ryan worries that the same thing will happen to him. In order to help, the Eigenoids transform him into a white blood cell so that they can confront the infamous Stephano, the staphylococcus aureus bacterium. Together they travel back in time to when Ryan had the splinter and go inside his body. There they learn about white lymph cells, phagocytes (who make up the White Ops), and bacteria, and they meet Charlie T, the White Duke of Cytes, and Big B-Cell. As Ryan realizes that his adventures with the Eigenoids have real consequences, he must learn to believe in himself and find the first cryton for the spell to save the Eigenoids. In this science fiction novel for middle readers, a boy journeys with a group of tiny magical beings within his body to learn and to save himself and his friends.