Within the week, Severus had met with Dumbledore, managed to return your thermos and set up a meeting that he was now going to attend. He glided smoothly out of the castle and headed for the Forbidden  Forest. He'd had one of the house-elves take Quirrell a note, asking to  meet him out there. It was better by far that they didn't have this  confrontation in the school itself, if only to avoid being overheard by  any students. The fact that everyone else was at dinner at the moment  was an added precaution. 

It didn't take him long to arrive at the clearing he'd specified  in the note. Quirrell was standing over by the far end, looking more  nervous than ever. Severus, however, sneered, not fooled in the slightest. At first he'd  thought Quirrell had been another sniveling professor, but ever since  the Slytherin/Gryffindor Quidditch match, he'd known better. And he had gotten Dumbledore's approval to pursue.

"Quirrell," he said coolly, stepping out into the clearing. 

"S-Severus--" the DADA professor replied.

"It's Professor Snape, to you." Severus' lip twitched in annoyance. That stutter could get extremely irritating.

"What d-did you want t-to t-talk about?" 

"A number of things," Severus answered. "The third floor corridor, and three-headed dogs, for instance." 

Quirrell's expression flickered. It was just for a moment, but it  was enough to let Snape know that he'd hit a nerve. It was also enough  to confirm that Quirrell was indeed up to no good. To others, maybe not, but certainly to him. 

"And Mr. Potter," Severus added, letting his tone get colder. 

Quirrell blinked. "Interesting t-topics. B-but I d-don't know why you wanted t-t-to meet here of all p-places, Severus..." 

Snape's voice was icy as he replied, "Oh, I thought we'd keep  this private. Students aren't supposed to know about the Sorcerer's Stone, after all." 

"S-surely you c-c-can't think that I--" Quirrell mumbled. 

Snape narrowed his eyes at him, making it clear that he knew perfectly well  that Quirrell was after it. Then he interrupted, hoping to catch the  other man at least a bit off-guard, "Have you found out how to get past  that beast of Hagrid's yet?" 

It seemed that he hadn't, Severus believed, with a certain amount of relief. If this man was some sort of master deceiver, it certainly wasn't good enough to fool him.

"B-b-but Severus, I--" 

Time to see if intimidation would still work. Taking a step  toward Quirrell, letting his height help with looming over the other  man, Snape said, "You don't want me as your enemy, Quirrell. And call me Severus again, we may just not need to find an answer to my questions, only a new Defense Against the Dark Arts professor." 

"I-I don't know what you--" 

"You know perfectly well what I mean," Severus replied coldly.  Perhaps if he gave a little added incentive... "Remember the Quidditch match, Quirrell? I'm sure that you'd prefer that Dumbledore  never heard about your little bit of hocus pocus." He gave Quirrell a  pointed look. It was a lie that Dumbledore didn't know, but Quirrell didn't need to know that. "I'm waiting." 

Quirrell tried to look puzzled, but didn't quite succeed. There was something in his eyes... "B-but I d-d-don't--" 

"Very well," Severus cut in abruptly. He wasn't in the mood to  listen to Quirrell deny everything and make excuses. He'd give the other  man a bit of time to think about the possible consequences, and then  reel him in. After all, as long as Quirrell didn't know how to get past  that miserable beast, the Stone was safe enough. "We'll have another  little chat soon, when you've had time to think things over and decided  where your loyalties lie." And if you do  make the mistake of deciding that they lie with Voldemort, I will take great  pleasure in turning you over to the Aurors. Especially with what you've  put me through trying to protect Potter.