It's Broadcast Day in Ms. Frizzle's class. Ralphie promised everyone he'd figure out what kind of show they should put on. But, Ralphie is sick and can't come to school. So, everyone climbs aboard the Magic School Bus, because if Ralphie can't come to class Ms. Frizzle's class will come to him! Join the class as they travel Ralphie's bloodstream to find out how germs make him sick and how his body can make him well again.