Specifically, it's right after Sir Orrin drove Bryagh off the nest, where he'd eaten all of the rest of the eggs and hatchlings. The last egg hatched into Gorbash, who promptly bonded with Sir Orrin. The two were inseparable from that moment onward (until, of course, Gorbash was given to Melisande).
Princess Melisande's request to her father to go join Peter on present day earth. Also counts as a Tear Jerker for those parents who can relate to how Carolinus must be feeling.
Melisande: May I join him father?
Carolinus: Of all questions, I feared that the most.