Author's note: As promised, here is the next chapter. It's a bit lengthier than usual, but it didn't seem appropriate to cut it earlier. I hope you enjoy it. I'm glad to see that this story still has an audience. Please review!

Warnings: Swearing

Disclaimer: I do not own Harry Potter. I referenced pages 261-265 of Harry Potter and the Prisoner of Azkaban while writing this.

The Shrieking Shack

The remainder of the term passed without incident, aside from some minor cauldron explosions—really, by this point in the year, the students should have been able to follow the instructions Severus wrote on the board. It wasn't like it was hard.

But regardless of however many brain cells the children may have been lacking, exam week began and an unnatural hush fell over the castle. Severus spent much of his free time in the staff room, where the teachers liked to trade both complaints and amusing anecdotes about their students. According to Filius, Potter had overpowered his Cheering Charm, and Weasley had succumbed to an hour-long giggling fit.

Minerva relayed a story told to her by Lupin, about Granger bursting from her Defence test in hysterics. It turned out that the girl's boggart was Minerva telling her she'd failed all her exams. The real deputy headmistress seemed amused by this, due to the sheer absurdity of the thought of Granger failing anything. To Severus, Granger's meltdown smacked of burnout. Severus should know, he lived in a state of burnout, and the only reason he wasn't melting down too was that he was older and had shit to get on with. Personally, he thought it was highly irresponsible to give a thirteen-year-old girl a Time Turner, no matter how many classes she wanted to take and how brilliant she might be. But Dumbledore was the one who'd gotten the final say about the Time Turner, and he was good at being highly irresponsible.

Come the third year Potions exam, Severus watched Potter with an air of vindictive pleasure. The dunderhead couldn't get his Confusing Potion to thicken; it looked like liquid slime and would be about as effective. Severus scribbled a zero onto his notes, just because he could.

It was after dinner when Severus knocked at the door to Lupin's office.

"Lupin, I have your potion," he called when there was no answer, "and I haven't got all night."

When his words were still met with silence, he opened the door anyway. The wolf was nowhere in sight, so he strode over to the desk and set down the goblet. A parchment caught his eye. It was a map of the castle, with a little dot identifying everyone in it. This was the item Potter had had when Severus caught him sneaking back from Hogsmeade, and this was what Lupin had taken back.

A quick glance told him that Dumbledore was in his office. The dot steadily moved back and forth; the headmaster was pacing. Minerva was in the staffroom with Pomona and Aurora Sinistra. Filius was walking down a fourth-floor hallway. And the dot that was Lupin was rapidly moving across the grounds, towards the Whomping Willow. It vanished out of sight. Severus didn't even take ten seconds to think about this before he turned and strode out the door.

A wad of shimmery fabric lay at the base of the Willow. Severus curled his lip, but pulled the Cloak around him. It was careless of Potter to leave the artefact lying around, almost as careless as it was of Dumbledore to give him the blasted thing. Before the Willow could unfreeze, he slipped into the passageway. It was smaller than he remembered it, but of course, the last and only time he'd been here, he was a helpless teenager. Now he was an adult, and not helpless in the least.

The sight that greeted him inside the Shrieking Shack was a mix of the expected and unexpected: There was Lupin, scruffy and tired-looking as always, and a shaggy, dirty man whose face Severus would have recognized anywhere. Sirius Black. Severus's old hatred suddenly flared up, like a pot of water bubbling over the edge and hissing on the burner. The intensity and speed at which it happened was even greater than he could have imagined. What he had not been expecting was the presence of Potter, Weasley, and Granger, although he shouldn't have been surprised. Every year had to end with drama when Potter was around, and getting a T in Potions didn't count. Dumbledore would override that anyway.

"… same year, you know, and we—er—didn't like each other very much," Lupin was saying as Severus approached. Apparently, Severus was the current topic of conversation. His fury went up a notch. He hated being talked about. "He especially disliked James. Jealous, I think, of James's talent on the Quidditch pitch."

Severus stifled a laugh. Jealous of James Potter for his Quidditch skills! As if he cared about that.

"Anyway, Snape had seen me crossing the grounds with Madam Pomfrey one evening as she led me towards the Whomping Willow to transform. Sirius thought it would be—er—amusing, to tell Snape all he had to do was prod the knot on the tree-trunk with a long stick, and he'd be able to get in after me. Well, of course, Snape tried it—if he'd got as far as this house, he'd have met a fully grown werewolf—but your father, who'd heard what Sirius had done, went after Snape and pulled him back, at great risk to his life."

Severus grit his teeth. James Potter had been saving his own skin, nothing more. And the "Marauders" had barely gotten a slap on the wrist for their little stunt.

"Snape glimpsed me, though, at the end of the tunnel. He was forbidden to tell anybody by Dumbledore, but from that time on he knew what I was."

"So that's why Snape doesn't like you," said Potter slowly, "because he thought you were in on the joke?"

Whether Lupin was in on it or not hardly mattered at this point; either way, it was impossible for the wolf to extricate himself from the situation. Enough was enough.

"That's right," Severus spoke up, pulling off the Invisibility Cloak and aiming his wand at Lupin.

Black leapt to his feet, and Potter jumped as though he'd received a huge electric shock. Granger screamed.

"I found this at the base of the Whomping Willow," Severus said, carelessly throwing the Cloak aside. He wanted to incendio it, but with Black in the room, other things took precedence. "Very useful, Potter, I thank you."

"You're wondering, perhaps, how I knew you were here?" he continued, mocking and triumphant. "I've just been to your office, Lupin. You forgot to take your potion tonight, so I took a gobletful along. And very lucky I did… lucky for me, I mean. Lying on your desk was a certain map. One glance at it told me all I needed to know. I saw you running along this passageway and out of sight."

"Severus," Lupin tried to begin.

"I've told the Headmaster again and again that you've been helping your old friend Black into the castle, Lupin, and here's the proof. Not even I dreamed you would have the nerve to use this old place as your hideout-"

"Severus," Lupin said more urgently, "you're making a mistake. You haven't heard everything—I can explain—Sirius is not here to kill Harry-"

"Two more for Azkaban tonight," said Severus. "I shall be interested to see how Dumbledore takes this… he was quite convinced you were harmless, you know, Lupin… a tame werewolf."

Truthfully, the bulk of Severus's discrimination was just against this particular werewolf, but present company didn't need to know that.

"You fool. Is a schoolboy grudge worth putting an innocent man back inside Azkaban?"

Thin, snake-like cords burst from the end of Severus's wand with a bang and twisted themselves around Lupin's mouth, wrists and ankles; Lupin overbalanced and fell to the floor, unable to move. With a roar of rage, Black started forwards, but Severus pointed his wand straight between Black's eyes.

"Give me a reason." He was so angry he wanted to yell for days, but his voice came out in a whisper, as though the back pressure from all that rage had burned out his lung capacity. "Give me a reason to do it, and I swear I will."

Black stopped dead. Potter shared a bemused look with his comrades. Weasley was fighting to keep hold of a struggling pet rat.

It was Granger who broke the stalemate, taking an uncertain step towards Severus and saying, in a very breathless voice, "Professor Snape, it- it wouldn't hurt to hear what they've got to say, w-would it?"

"Miss Granger, you are already facing suspension from this school," Severus spat. "You, Potter, and Weasley are out of bounds, in the company of a convicted murderer and a werewolf. For once in your life, hold your tongue."

"But if- if there was a mistake-"

"Keep quiet, you stupid girl! Don't talk about what you don't understand!" A few sparks shot out the end of his wand, emotionally-charged magical power itching to be released on Black, the scum who had sold out Lily Potter. Granger, blessedly, fell silent.

Severus took a breath. "Vengeance is very sweet," he said, collected again. "How I hoped I would be the one to catch you." Well, in his mind he'd actually skipped the part where Black was caught and went directly to imagining him getting Kissed in vivid detail, but close enough. It didn't matter who caught the man, as long as the end result was still the same.

"The joke's on you again, Severus," snarled Black. "As long as this boy brings his rat up to the castle"—he jerked his head at Weasley—"I'll come quietly."

"Up to the castle? I don't think we'll need to go that far. All I have to do is call the Dementors once we get out of the Willow. They'll be very pleased to see you, Black… pleased enough to give you a little kiss, I daresay."

And there was the reaction he'd been looking for. What little colour there was in Black's face left it.

"You- you've got to hear me out," he croaked. "The rat—look at the rat—"

But Severus was beyond listening to any sort of reason. He despised Black. Black was arrogant and loud and obnoxious, and when they'd been students, he'd made Severus's life hell, just because Severus was friendless and scrawny and poor and half-blooded. Just because he'd had the popularity, the power.

Well look who has the power now, Severus thought.

Plus, Black was a traitor. Severus didn't have to like either of the men involved to recognize that selling out your best friend was horrible, especially when it was literally life or death. Even Severus had more loyalty than that, and he'd been a fucking Death Eater. At least he could say he hadn't known what he was doing. Black had no such alibi.

"Come on, all of you," he said. He clicked his fingers, and the ends of the cords that bound Lupin flew into his hands. At the back of his mind was the thought that Lupin hadn't taken his potion tonight. It made him nervous, though he'd deny it to the death. "I'll drag the werewolf. Perhaps the Dementors will have a kiss for him, too."

At that, Potter crossed the room and blocked the door.

"Get out of the way, Potter, you're in enough trouble already," Severus snarled. "If I hadn't been here to save your skin—"

"Professor Lupin could have killed me about a hundred times this year," said Potter. "I've been alone with him loads of times, having defence lessons against the Dementors. If he was helping Black, why didn't he just finish me off then?"

"Don't ask me to fathom the way a werewolf's mind works. Get out of the way, Potter."

"You're pathetic! Just because they made a fool of you at school, you won't even listen—"

"Silence! I will not be spoken to like that!" This was why he had been so angry with Dumbledore earlier. People knowing about his past made him feel humiliated. It made him hate himself. "Like father like son, Potter. I have just saved your neck, you should be thanking me on bended knee. You would have been well served if he'd killed you. You'd have died like your father, too arrogant to believe you might be mistaken in Black—now get out of the way, or I will make you. Get out of the way, Potter!"

The next thing he knew, there was shouting. and Severus was lifted off his feet and slammed into the wall, and he was out like a light.