"I shall have a bowl of green lentil soup, with soy sauce," Professor Quirrell said to the waitress. "And for Mr. Potter, a plate of Tenorman's family chili."
Harry hesitated in sudden dismay. He'd resolved to stick to vegetarian dishes for the moment, but he'd forgotten in his deliberations that Professor Quirrell did the actual ordering - and it would be awkward if he protested now -
The waitress bowed to them, and turned to go -
"Erm, excuse me, any meat in that from snakes or flying squirrels?"
The waitress didn't so much as blink an eye, only turned back to Harry, shook her head, bowed politely to him again, and resumed her walk toward the door.
(The other parts of Harry were snickering at him. Gryffindor was making sardonic comments about how a little social discomfort was enough to get him to resort to Cannibalism! (shouted by Hufflepuff), and Slytherin was remarking on how nice it was that Harry's ethics were flexible when it came to important goals like maintaining his relationship with Professor Quirrell.)
After the waitress had closed the door behind her, Professor Quirrell waved a hand to slide home the locking bar, spoke the usual four Charms to ensure privacy, and then said, "An interesting question, Mr. Potter. I wonder why you asked it?"
Harry kept his face steady. "I was looking up some facts about the Patronus Charm earlier," he said. "According to The Patronus Charm: Wizards Who Could and Couldn't, it turns out that Godric couldn't and Salazar could. I was surprised, so I looked up the reference, in Four Lives of Power. And then I discovered that Salazar Slytherin could supposedly talk to snakes." (Temporal sequence wasn't the same as causation, it wasn't Harry's fault if Professor Quirrell missed that.) "Further research turned up an old story about a mother goddess type who could talk to flying squirrels. I was a bit worried about the prospect of eating something that could talk."
And Harry took a casual sip of his water -
- just as Professor Quirrell said, "Mr. Potter, would I be correct in guessing that you are also a Parselmouth?"
When Harry was done coughing, he set his glass of water back down on the table, fixed his gaze on Professor Quirrell's chin rather than looking him in the eyes, and said, "So you are able to perform Legilimency through my Occlumency barriers, then."
Professor Quirrell was grinning widely. "I shall take that as a compliment, Mr. Potter, but no."
"I'm not buying this anymore," Harry said. "There's no way you came to that conclusion based on that evidence."
"Of course not," Professor Quirrell said equably. "I had planned to ask you that question today in any case, and simply chose an opportune moment. I have suspected since December, in fact -"
"December?" said Harry. "I found out yesterday!"
"Ah, so you did not realize the Sorting Hat's message to you was in Parseltongue?"
The Defense Professor had timed it exactly right the second time, too, just as Harry was taking a gulp of water to clear out his throat from the first coughing fit.
Harry hadn't realized, not until just now. Of course it was obvious the instant Professor Quirrell said it. Right, Professor McGonagall had even told him not to talk to snakes where anyone could see him, but he'd thought she'd meant not to be seen talking to any statues or architectural features in Hogwarts that looked like snakes. Double illusion of transparency, he'd thought he understood her, she'd thought he understood her - but how the hell -
"So," Harry said, "you performed Legilimency on me during my first Defense class, to find out what happened with the Sorting Hat -"
"Then I would not have found out in December." Professor Quirell leaned back, smiling. "This is not a puzzle you can solve on your own, Mr. Potter, so I will reveal the answer. Over the winter holiday, I was alerted to the fact that the Headmaster had filed a request for a closed judicial panel to review the case of one Mr. Rubeus Hagrid, whom you know as the Keeper of Keys and Grounds at Hogwarts, and who was accused of the murder of Abigail Myrtle in 1943."
"Oh, of course," said Harry, "that makes it downright obvious that I'm a Parselmouth. Professor, what the sweet slithering snakes -"
"The other suspect for that murder was Slytherin's Monster, the legendary inhabitant of Slytherin's Chamber of Secrets. Which is why certain sources alerted me to the fact, and why it caught my attention sufficiently that I spent a good deal of bribe money to learn the details of the case. Now in point of fact, Mr. Potter, Mr. Hagrid is innocent. Ridiculously obviously innocent. He is the most blatantly innocent bystander to be convicted by the magical British legal system since Grindelwald's Confunding of Neville Chamberlain was pinned on Amanda Knox. Headmaster Dippet prompted a student puppet to accuse Mr. Hagrid because Dippet needed a scapegoat to take the blame for the death of Miss Myrtle, and our marvelous justice system agreed that this was plausible enough to warrant Mr. Hagrid's expulsion and the snapping of his wand. Our current Headmaster needs merely provide some new item of evidence significant enough to reconvene the case; and with Dumbledore applying pressure instead of Dippet, the result is a foregone conclusion. Lucius Malfoy has no particular reason to fear Mr. Hagrid's vindication; thus Lucius Malfoy will only resist to the extent that he can do so costlessly in order to impose costs on Dumbledore, and Dumbledore is clearly willing to prosecute the case regardless."
Professor Quirrell took a sip of his water. "But I digress. The new evidence that the Headmaster promises to provide is to exhibit a previously undetected spell on the Sorting Hat, which, the Headmaster asserts, he has personally determined to respond only to Slytherins who are also Parselmouths. The Headmaster further argues that this favors the interpretation that the Chamber of Secrets was indeed opened in 1943, approximately the right time frame for He-Who-Must-Not-Be-Named, a known Parselmouth, to have attended Hogwarts. It is a rather questionable logic, but a judicial panel may rule that it swings the case far enough to bring Mr. Hagrid's guilt into doubt, if they can manage to keep a straight face as they say it. And now we come to the key question: how did the Headmaster discover this hidden spell on the Sorting Hat?"
Professor Quirrell was smiling thinly now. "Well now, let us suppose that there was a Parselmouth in this year's crop of students, a potential Heir of Slytherin. You must admit, Mr. Potter, that you stand out as a possibility whenever extraordinary people are considered. And if I then further ask myself which new Slytherin would be most likely to have his mental privacy invaded by the Headmaster, specifically hunting the memories of his Sorting, why, you stand out even more." The smile vanished. "So you see, Mr. Potter, it was not I who invaded your mind, though I will not ask you to apologize. It is not your fault that you believed Dumbledore's protestations of respecting your mental privacy."
"My sincere apologies," Harry said, keeping his face expressionless. The rigid control was a confession in its own right, as was the sweat beading his forehead; but he didn't think the Defense Professor would take any evidence from that. Professor Quirrell would just think Harry was nervous at having been discovered as the Heir of Slytherin. Rather than being nervous that Professor Quirrell might realize that Harry had deliberately betrayed Slytherin's secret... which itself was no longer seeming like such a smart move.