12-year-old Joe has a secret he has never told anyone. For as long as he can remember, Joe has wanted to study the moon. He's worried that something bad might happen to it and then it will have to go away, so he wants to learn how to protect it.

Joe will be spending the summer with his Aunt Myra in Midville. Joe is nervous about the visit. He doesn't want to leave his friends because he's worried that they will forget about him. But, upon Joe's arrival, he discovers that Midville isn't so bad. And it doesn't hurt that Aunt Myra's neighbor, 12-year-old Beatrice, is beautiful and wants to spend time with him!

One fateful day, Joe and Beatrice meet Mr. Boulderwall, one of the richest men in the world. Mr. Boulderwall also has a secret. He needs to find someone to run his company when he retires, and he decides that Joe is the perfect candidate! But this would mean that Joe wouldn't be able to help the moon. He would have to focus on business instead.

Can Joe admit that his love of the moon is more important than wealth? Or will Joe keep his secret for the rest of his life and never tell anybody about his dream? Find out in The Moon Over High Street by Natalie Babbitt.