Look, I admit, I'm no Boxcar Children scholar. I probably read about 20 of these, and I only have clear memories of one. So there's every possibility that this is, in fact, a picture of a bicycle mystery. It is possible, even likely that Henry is not pointing at the mysterious house, but at a nearby mysterious bicycle. Or he's stretching to get ready to point at his bike. Or his hand is exhibiting a natural aversion to Violet's jodhpurs. Of course, the far more likely answer is that "The Spooky House Mystery Which Was Noticed While On Bicycles" just doesn't have the same punch.