Unicorn blood.

Dumbledore rubbed his forehead. There were many uses for it, none of it good. "Thank you, Severus. This just confirmed my suspicions."

"Quirrell?" the potions master asked sharply.

Dumbledore thought a moment and then shook his head. "Doesn't seem strong enough to kill a unicorn, does he?"

Snape shuddered at the thought. "If Lord Voldemort was controlling him, Headmaster," he said frankly, "a man will do anything to obey."

Dumbledore looked up bleakly and then his face lit into an admiring smile, making Snape a bit uncomfortable at having that admiration aimed at him. "Most men, anyway, Severus. I'm proud to say that you are not most men. I know I have told you how much I appreciate your help during those dark times but let me say it again. I admire your strength, Severus, and I'm glad you are with me now."

Snape gave a nod and he actually smiled a genuine smile. There was nothing like feeling appreciated and admired by a man of Dumbledore's stamp. "Thank you, Headmaster," he said modestly and left the office.

"See?" Dumbledore said to the corner of the room. Lupin's face came from the shadows. "I told you so."

"He's changed," commented Lupin.

"Yes, deep down he has, but the old rascal still lurks on the surface." Dumbledore gave a huffy chortle. "He can be trusted, Remus."

"So I see," Lupin said.

Snape already knew it, but this just confirmed it.

The world hated him.

Quirrell's clandestine activities seemed to have halted as suddenly as they had begun at the beginning of the year. Everytime Snape checked up on him or tried to bully him, Quirrell was exactly where he was supposed to be. After reporting to Dumbledore these perplexing events, the headmaster merely heaved a heavy sigh, told him to never mind and to get ready for final exams. Frustrated, Snape complied, taking his aggravation out on his students. He took great delight in threatening them all making the final exam on the Forgetfulness Potion, the hardest any of the first years had ever faced. The higher classes got equal treatment.

Dumbledore caught him again later in the final exam week with Professor McGonagall in tow. "Severus, I have to go to the Ministry this evening. Some important emergency they have to discuss with me. I'm leaving you and McGongall in charge of keeping an eye on things. You know who to keep an eye on, am I correct?"

Snape's black eyes met Dumbledore's watery blue ones and gave a sharp nod. "I know," he said and McGonagall snorted. Snape didn't trust this trip of Dumbledore's and from the look in Dumbledore's eyes, he didn't either.

"Don't be blaming Potter for everything, Severus," she said crisply, mistaking the meaning of 'who'.

Snape gave her a baleful look. "You don't discipline him enough, Minerva," he growled peevishly. "He thinks he can get away with murder, just like his father." He knew immediately it was the wrong thing to say when Dumbledore's face darkened.

"Enough!" the headmaster rumbled. "I will hear no more of this talk about a student, past, present or future, is that understood, the both of you?" Snape and McGonagal nodded, dumbstruck. Dumbledore rarely lost his temper. "Good, now you have students to attend and I want to double check our failsafes one last time before I leave. All will be well, my friends."

Snape and McGonagall glared at each other before stalking away in opposite directions. Snape's disposition soured even more when he stumbled across Potter, Weasley and Granger talking about him on the way to his office an hour later.

"It's tonight," Potter was saying feverishly. "Snape's going through the trapdoor tonight. He's found out everything he needs, and now he's got Dumbledore out of the way. He sent that note, I bet the Ministry of Magic will get a real shock when Dumbledore turns up."

Hermione turned a bit more to face Potter as she spoke. "But what can we..." Her voice trailed off into a gasp when she noticed the object of their conversation standing behind her. The two boys whipped around and their jaws dropped.

Snape's lip curled and he fought the urge to box all their ears. How dare they think he would betray Albus Dumbledore! The nerve! He would lay his life down for the headmaster! He quickly collected himself and stated cooly, "Good afternoon."

They continued gaping at him.

"You shouldn't be in on a day like this," he continued smoothly, though inside he was trembling with rage. He'd risked his life to bring information to defeat Voldemort to Dumbledore and now they suspected him of conspiring with the Dark Lord!

"We were.." Potter began uncertainly but Snape cut him off.

"You want to be more careful. Hanging around like this, people will think you're up to something. And Gryffindor really can't afford to lose any more points, can it?" He made the last comment with sadistic pleasure, watching the three of them purple with anger. 'Go on, blow up at me, Potter. Do it!' Instead the three of them turned to go outside.

Snape had sudden inspiration. The book that screamed mysteriously in the night and the fact that no one saw the three of them enter the upstairs that night but Filch caught them leaving seemed to click an old memory of James Potter's exploits at Hogwarts. 'The invisible cloak,' Snape thought.

"Be warned, Potter." The three of them turned back to him politely. "Anymore nighttime wanderings and I will personally make sure you are expelled." Satisfied that Potter understood his warning from his wide green eyes, Snape swept away with a curt, "Good day to you."

"What are you doing?" Snape stumbled into Hermione Granger a few hours later as she hovered outside the teacher's lounge.

She looked at him startled and worried. "I-I," she swallowed and took a breath. "I was waiting on Professor Flitwick. I'm worried about how I did on my exam in his..."

"Fine," Snape interrupted. "I'll go find him. Stay put."

"Yessir," she murmured.

He stepped in and grabbed Flitwick's robe. "Student to see you," he rasped with no little humour. There was ever little chance of a student hanging after his robes, begging for clues on scores. Snape was well-known for marking down instead of up. He all but flung Flitwick at Granger and walked away, satisfied at having done a good deed (so to speak) for the day. He went back to his rooms and settled down for a nap.

It was going to be a long night with the headmaster gone.