Draco'd had to be enervated after the Dark Lord had left. Even after, it had taken him a few minutes of shaking on the floor before he could even stand or speak. Finally, Severus had simply left the boy alone, and Draco had managed to sit and eventually stand on his own. Still wobbling, Draco made it to a chair next to a table and collapsed onto it. Severus silently gave him a glass of water – prolonged cruciatus tended to become more painful by draining the body of its moisture. After several glasses, Draco sat back, barely trembling anymore.
"When the Dark Lord asks," Severus offered, by way of apology.
Draco nodded. "Naturally." All those exercises had not been for naught; although he'd been slow to see progress at first, Draco's natural secrecy and mental discipline had ensured a natural aptitude for the hidden art of occlumency. Since his Master had last examined him, progress had been extremely rapid. Draco finally felt in command of himself; enough so that the thought of venting his rage to Snape passed gently and almost unnoticed through his mind before storing itself away for another occasion.
"There is another purpose to this visit," Snape began. "Your mother recently expressed her concern that you and I had become distant. She was possessed of the notion that, given our long relationship and your father's unavailability, I should attempt to remain close to you." Snape paused, and gave one of his often-used weary-of-idiots looks. "Despite your behavior of late. And here I'd thought I'd had my last of mothers' blind spots for their children after I could no longer teach." Draco felt a gentle poke at his mind.
You took my job, Draco thought. You made me look bad to the Dark Lord. He thinks I'm a traitor because of you. He threatened to kill me because of you.
Then Draco thought he might have overplayed his lack of concern for his parents.
He threatened my parents because of you, he added.
"I apologize for her, and for myself," Draco spoke politely. He and Snape locked eyes, and when they looked away only Draco felt triumphant. He knew about the vow, which made it slightly unclear where Snape aligned himself, but certainly not unclear enough to give the impression that Draco was anything but satisfied in the Dark Lord's service.
Snape pretended to be mollified just as Draco pretended to be repentant. Then the former switched tactics. He leaned in, and spoke in a low voice,
"Do you know why I did it?"
Draco was ready for this one. "I know you made an unbreakable vow. You were saving yourself. Oh, and me – thanks for that, by the way," Draco added insolently.
"You missed one." Draco once again locked eyes with Severus. "I also did it because I support Lord Voldemort and desire nothing more than his triumph over all the half-wit blood-traitors and disgusting mudbloods who oppose him."
Draco was thrown for a moment. "I didn't think it necessary to include – like telling you that you breathe in order to survive."
Snapes eyes flashed. "Perhaps I breathe because I like breathing, boy. Perhaps I breathe that I might cause unworthy witches and wizards to stop breathing! In any case, take care not to question my loyalty again, and I shall take care to hide from the Dark Lord the thoughts I discovered in you on the night of Dumbledore's death."
"On the night you killed Dumbledore," Draco corrected cautiously. You don't want to say it out loud, do you, Draco thought to himself (rather loudly).
"Yes, when I killed him!" Snape yelled furiously. "When I acted, instead of, for example, hoping someone else would so I wouldn't have to! Or, perhaps, wondering if I could take Dumbledore's offer to shield me and my family from the sight of my Master! Do you ever listen, boy?"
Draco carefully allowed one last defiant 'more closely than you wish, I'll bet' to pass through his mind before sealing off his anger and conceding Snape's superior position.
"You're right, sir. I lingered. I was uncertain. It won't happen again."
"No," Snape agreed, begrudgingly offering Draco a glass of wine and starting on one himself. "I can see that." And Draco, as inexperienced a legilimens as he was, was able to ferret out a note of disappointment, which he quickly stored away to consider in the future.