Severus looks like he might say something in immediate response to Narcissa - but then catches sight of the older Lucius and. Doesn't. He gives him a look for a moment that reads Well of course there's two of you in this room and now if you get too close reality will implode upon itself, great before flicking his gaze back to his inebriated hostess.

"I must grudgingly point out that he is merely the messenger, in this instance."