As their family begins to pack up their home and prepare for a move, Simon is certain that his baby sister just does not want to leave everything she knows behind.

Simon hates the idea of moving, but he insists that it's his baby sister, Maggie, who doesn't want to go. After all, Simon points out, the place won't have a slide like the one Maggie is used to, and her furniture just won't look right in her new room.

But once Simon gets a glimpse of the pond near his new house and meets his teacher and classmates, he starts to think that maybe Maggie won't mind moving after all....