"It suits me if it suits you," Byerly responds. "That - " And then he catches sight of his erstwhile assistant, and says, "Ah."

Then he raises a hand and calls out, "Hallo, Artemaeus! Come here, come here." Though he also steps in front of Octavius, keeping him from view, so that Artemaeus (still not especially subtle, despite By's best efforts to make the boy into a fellow weasel) won't have a chance to react while in the midst of others.