Evan loves being big brother to Sam and Finn. They do everything together—go fishing, climb trees, and play astronauts. But lately, Evan notices that he and Sam don’t look like brothers anymore. Sam wants to have long hair, and even asks to wear a dress on the first day of school. As time goes by, Evan comes to understand why Sam wants to look like a girl—because Sam is a girl. Sam is transgender. And just like always, Sam loves to dream with Evan and Finn about going to the moon together.