Alec Valorian looked at his master and noticed his hand balled into a fist. Just from seeing his expression, he already knew how displeased the Crown Prince was from the way the King of Antares was talking to him.
He was relieved that Chance held back and did not react badly to the taunts that King Cadell was giving him. If he had reacted badly, the King will get even more suspicious and things might turn for the worst.
When they were about to leave, the Valorian knight saw the look on Chance's face when the King said he heard a lot of things about his stay in Canopus. Seeing how his face has darkened, Alec got the idea that the Crown Prince had already figured out about the fact that there was someone spying on him.