Showing How the Golden Dustman Helped to Scatter Dust
Apparently, Mr. and Mrs. Boffin have known that Mr. Rokesmith was actually John Harmon for some time. Mrs. Boffin figured it out one night when the light of a fireplace caught John's face in a way that made him look like the little boy Mrs. Boffin used to take care of.
They sit Bella down and break the news. She had no clue.
From the moment the Boffins knew, Mr. Boffin decided to act like a jerk and to pretend that his money was making him evil. But why go to all this trouble, you ask?
Because John Harmon wanted to make sure that Bella Wilfer had a good heart, deep down. She ended up passing his test when she chose him over the Boffins' money.
Now you might be saying, "Hey, this is a pretty lousy thing to do to Bella." And you'd be right. But readers in Dickens' time probably didn't see anything wrong with it.