The kids in room 3B have found out their teacher is engaged! But who's the lucky groom? Harry goes into detective mode to find out, and Doug is willing to help-until he sees Harry stealing a piece of evidence! Doug can't believe what Harry has done, but Harry thinks his risky move is worth it. After all, he cracks the case and tells everyone who Miss Mackle is going to marry. but does Harry have his facts straight? Or has he made a horrible mistake?