Leon solves the mystery - Topsy Smith (First edition)

Life at Clan College was never dull. Rivalry between the Houses and between individuals was a constant source of "incidents". With pranks and practical jokes added, there was little occasion for boredom. 

But when an innocent prank becomes a link in a chain of mysterious events the consequences may be unpredictable. There was little harm, for instance, in Leon and his friends raiding Fatty Wilson's tuckbox. He was so mean that, in a way, he deserved it. And Fatty could even be excused for calling the other inmates of the dormitory a bunch of crooks. 

But then, one morning, Pietie woke up to find his new gold watch gone. A few nights later more articles disappeared from the dorm. After putting their heads together the boys came to a rather unpleasant conclusion: the thief must be somebody in the dorm!

To everybody the unpopular Fatty Wilson seemed the most likely culprit. Leon, too, did not escape suspicion, because he was a poor boy.

Leon decided that something had to be done - and this is when things really started happening.