These are Phineas L. MacGuire's (a.k.a. Mac) goals for 4th grade: 1. To be the best fourth grade scientist ever. 2. To be the best fourth grade scientist ever. 3. To be the best fourth grade scientist ever. It's a tall order, but he's confident that he can achieve his goal, especially since Aretha has asked him to help her earn a Girl Scout badge by creating the mold that produces penicillin. After all, who knows more about mold than Mac? And how many fourth graders can say that they've reproduced penicillin? None, as far as Mac knows. But the school year gets busier when he has to manage Ben's class president campaign deal with his new babysitter, Sarah Fortemeyer, the Teenage Girl Space Alien from the Planet Pink. How is he supposed to focus on mold now?