Disclaimer: I am not J.K. Rowling and I don't own anything.
(Apologies for the lack of updates recently. I realise this is a very short chapter, but I'll do my best to post another one in a couple of days)
Severus didn't sleep a wink that night, expecting some measure of revenge from his housemates over the Rosier incident. They had so far stuck to completely ignoring him, but he knew something was coming, and it was bound to be worse than anything they had subjected him to so far. Still, nothing happened all that night, and when he checked his personal effects in the morning, they all still appeared to be intact as far as he could tell. Perhaps they intended to increase his nervousness by making him wait.
If so, all the more reason to act quickly.
At breakfast, Severus managed to catch the headmaster's eye, and took this opportunity to confirm his agreement to the plan by nodding at him almost imperceptibly. From the small smile that then graced the older man's lips, it was clear that he had succeeded in making himself understood. The game was afoot.
The first step was to get Lucius alone. He had a good deal of influence, and, having all the calculating level-headedness of a snake, was the most likely to listen to him without anger.
He got his opportunity that evening: as they were going into the common room after dinner, he and Lucius found themselves the last two waiting to go in. Desperate to make the most of this chance to speak to him alone, Severus turned to him and said, in as nervous and embarrassed a tone as he could manage, "Malfoy – may I have a quick word with you?"
The older boy turned to him with raised eyebrows, and replied, "Ah, Snape. What is it?"
Severus took a deep breath, and launched into the tirade he had planned: he was awfully embarrassed at the way he had behaved lately, and could not believe he had so easily turned into a traitor, all over some – some little mudblood; he finally saw Lily Evans for what she was – an ungrateful little tramp – and could not understand how he could ever have fancied her (he did his best to convey all the resentful rage of spurned love and wounded pride as he spoke of her); he had been such a fool, etc., etc. Most importantly – what, if anything, could he do to redeem himself?
He had not found it pleasant or easy to rage against Lily in this way, and so was greatly relieved when Lucius, just as he had hoped, slowly smiled his best scheming smile, and laid a big-brotherly hand on his shoulder. Severus successfully suppressed the urge to flinch away in disgust, and, as he looked into his face, did his best impression of a penitent, grateful underling.