I should start by saying that I have heard of The Hardy Boys before; if you haven’t I think they are like The Famous Five but in America and without girls, transvestites or dogs. The title makes this sound quite ambitious for a book for children as a clock can tick for quite a long time especially a grandfather clock which was started by your grandfather because he couldn’t afford a digital watch.
However I don’t believe that your grandfather has a legal obligation to live behind the grandfather clock which might be why the two boys look so surprised that this is what he does. I don’t know why grandfather would want to tie them up, either. It’s possible the painting is misleading and they’re just covering their mouths because he smells weird and musty like old people do when some bits of them die too early or they forget what a bath is.
I think this book might be quite frightening for small children as they would expect their grandfather to live behind a clock and smell a bit like death so I would not let them look at it or tell them about it. I also do not like the colour selected for the name of the author as it makes it quite hard to read and that’s Franklin disrespectful (this is a pun I should have written frankly disrespectful but the author’s name is Franklin so I swapped them).
If they still make new ones of this book they should change the grandfather clock to a modern day clock, like that one that projects the time onto the ceiling with lasers so you know what time it is even if you are lying down.