Lucius' temperament might have intimidated others, especially where the elves were concerned, but his short fuse did not cause her to step back or cower in the slightest. Narcissa knew her husband's temper, and she also knew he would never let it escalate to the point where he would actually harm her.
"No, I suppose it's not your fault, is it?" She mused out loud, almost without even realizing she'd spoken her thoughts. There was a slight bitterness to her tone, though she hadn't meant for it to sound that way. The truth was, it was irritating to her that he was not taking any sort of responsibility for the situation. Maybe he hadn't personally had a hand in the most recent incident to have occurred, but could he not acknowledge having any part in what was happening? Even Narcissa blamed herself for their son's pain and not being able to protect him from it.
With delicate hands, she picked up the book he'd discarded and moved to put it back in its proper place. Sadly, she'd gotten into a habit of picking up after others; with all of their house guests, the elves had a difficult time keeping up. "I would much prefer trying to help ease your tossing and turning. For future reference."