The theme is the mystery of the missing mile-high cake.

The mystery of the missing mile-high cake, as a theme, introduces students to the concept of a thrilling and engaging plot centered around the search for a cake that has mysteriously disappeared. To understand this theme thoroughly, it's important to follow a logical progression:

1. Introduction of the cake: The narrative begins by introducing a cake that is notably mile-high, an exaggeration to signify its grandeur and importance.

2. The Disappearance: At some point in the story, it is revealed that this remarkable cake has gone missing, presenting the central mystery and conflict of the theme.

3. Investigation: Characters in the story, possibly including clever detectives or curious bystanders, would then embark on a quest to solve the mystery. This part of the theme involves gathering clues, interviewing witnesses, and employing deductive reasoning to figure out what happened to the cake.

4. Revelation: As the theme unfolds, the reasons behind the disappearance start becoming clear through the clues and evidence gathered.

5. Conclusion: The story will typically conclude with the mystery being resolved, revealing who took the cake and why, followed by a fitting resolution to the storyline.