If Charls had any less restraint than he trained himself to put on at all times, that sigh, that hidden groan might have escaped him and he would berate himself harshly. Manners, they were very important to Charls. As it was, he managed to succeed to...more or less hide this from Isaiah, rewarding him with a stare and the slight tension of his lips turning to a line. He didn't need a distraction, Blair didn't need a distraction.
Isaiah was being polite, though, and nothing of the man's presence, smile and all, seemed overbearing enough to force Charls to bare teeth at him. So after another hidden sigh (one best accompanied by the rolling of his eyes), he said, "It's warm." And nothing else.
One of his tablets had lit up and he glanced at it. He would have taken it to read whatever it was that wanted his attention but it was, well, rude to turn away from a man he was half-expecting to be on his way soon.