Story: Ralphie is sick and has to stay home from school. So Ms. Frizzle and the class take The Magic School Bus to Ralphie's bedroom. They shrink and go inside his body, and travel in his blood stream to his sore throat. The kids find out what's making Ralphie sick, and see his white blood cells fight the bacteria in a raging battle. But then the white blood cells think The Magic School Bus is a germ. How can the class escape?