This is a story about a small crime in a primary school. It's hardly worth bothering about, but it worries Charlie Thomson. After all, Charlie's the one who got the blame. So he sets out to do some detective work and find the real culprit, then clear his name.
The tale has all the elements of a proper detective yarn, a whodunit. It has a crime and suspects with motives, means and opportunities. It also has a detective, who happens to be Charlie Thomson.
It also has clues for the sharp-eyed reader to spot. And this story, like all good mystery yarns, also has a denouement — the bit at the end where the detective unmasks the real culprit.