The story follows Steve and Joe through their childhood. After school, the two of them go stay at a magical house, where everything is alive and joyful. Joe has no friends at school. None of the other kids understand him, least of all his brother. Joe doesn't care; he has friends at the Blue's Clues house.
At seven years old, Joe starts feeling lonely. He and mailbox have aged normally, but the rest of their friends have stayed young. Soon he's cut off from the magic house and those within it. Without a friend in the world, Joe wants to rely on Steve for support, but is jealous of the attention he gives Blue. Joe isolates himself, growing distant as the years pass.
Believing in Magic provides examples of:
- Age-Appropriate Angst: Steve leaving home is the last straw for 11-year-old Joe, partly because Steve said he'd always be there for him.
- Alternative Character Interpretation: A lot of it, for both Steve and Joe. In-universe
- Backstory: For Steve and Joe, and more specifically, Joe's introduction arc.
- Big Brother Instinct: When Joe is in second grade, Steve feels responsible to protect him from bullies.
- Black Sheep: Joe
- Coming-of-Age Story: For Joe and finally Steve.
- Dark and Troubled Past
- Deconstruction: Of the Blue's Clues arc that introduced Joe.
- Heartbreaking In Hindsight: In Joe's story, we see that Joe is horribly overreacting to Steve leaving home. In Steve's story, we see Steve promising he'll always be there a few years earlier.
- In-Joke: Joe's coach addresses him as "Burns". Steve's actor in the original Blue's Clues was Steven Burns.
- Manchild: Steve grows to be one while living in the Blue's Clues house.
- Security Blanket: Boris, Joe's toy duck from Blue's Clues is shown to have been this.
- Switching P.O.V.: The first chapter follows major events in Joe's childhood, the second chapter Steve's. The third follows both of them.
- The Promise: Steve to Joe— "You've always got me, all right?"
- The Runaway: Joe, at 12 years old. It's never really shown if his family found him.
- Watching the Sunset: Described as an "unfortunate ritual" for Joe. It reminds him of the day he ran away.
- What Happened to the Mouse?: We never see Mailbox again after his first scene.