OK, read this exchange between Phineas and Gene:
"Isn't the bone supposed to be stronger when it grows together over a place where it's been broken once?"
"Yes, I think it is."
"I think so too. In fact I think I can feel it getting stronger" (11.15-7).
As you might have guessed, they're not just talking about the bone. They're talking about their friendship. The ever-optimistic Phineas believes that, having suffered a break in their relationship (betrayal, suspicion, confession), the boys have patched things up (forgiveness) and their friendship is now stronger than ever. This is…dubious, to say the least. Finny's leg is much weaker now than it was before, as demonstrated in a few chapters by fall #2. So we have to ask whether the same is true of their friendship, if it, too, is weakened by the break. What do you think?