Chapter 1: In Which Rats Become Slugs, and Sirius Gets Suspicious

A/N: This hit me over the head when I re-read Prisoner of Azkaban while I was on vacation. I borrowed my dad's laptop every day until it was done. I intended it to be a short story, but it got really long so I decided to split it up a little bit. This was the result. It's now been revised a bit to match with Half-Blood Prince, so please watch out for spoilers. I've also polished some scenes and tweaked some characterization, so it should be a better read.

Speaking of revision, I haven't got a clue when Voldemort came to ask Dumbledore if he could teach DADA as compared to when the Marauders were at school, so I had an interesting time deciding how to handle that aspect of the story. None of the timelines I looked at gave any conclusive answers and unfortunately I don't have a copy of Half-Blood Prince on hand to re-read the scene. So I did the best I could, and left it open to both possibilities - it could have been pure coincidence that their professor wasn't there for three years in a row, or it could be the curse.

Disclaimer: I'm not profiting off this at all, and I don't own the characters. This is all just fun and speculation.

"Boggarts like dark, enclosed spaces," said Professor Lupin. "Wardrobes, the gap beneath beds, the cupboards under sinks--I've even met one that had lodged itself in a grandfather clock..."

"It's always best to have company when you're dealing with a boggart. He becomes confused. Which should he become, a headless corpse or a flesh-eating slug? I once saw a boggart make that very mistake--tried to frighten two people at once and turned himself into half a slug. Not remotely frightening."

Remus watched with a smile on his face as his third year students filed out, talking excitedly about the boggart they had just vanquished together. He knew Snape wouldn't be very pleased with him, but Remus hadn't been able to resist the chance to get back at the man who still carried a grudge after all these years. Although it wasn't entirely his fault - how was he supposed to know that Snape would be the boy's worst fear? Yet somehow, Remus didn't think the other professor would see it that way. He fully intended to stay out of Snape's way for a while. Remus quietly left the staff room and retreated to his office, carefully avoiding the other teachers, especially Snape.

Remus couldn't help but doubt the wisdom of making Snape a teacher. Neville would be an excellent student, if he just had a little more confidence - and Snape seemed intent on making sure he never had a shred. It was biased, unfair and cruel - but then, when had Snape been any different? Remus sighed. He knew too well the truth of that particular thought.

Well, he had his work cut out for him, Remus decided. But Neville would learn soon enough, and he was already on his way. There was nothing like vanquishing your fears to give you a little ego boost. He smiled at the thought of Snape in a dress. Sirius would have been proud of that one.

Remus' smile froze and dropped off his face. Sirius. No. Black. Never Sirius. Always Black. Thirteen years, and he still couldn't stop thinking about the bastard. What would it take for him to get over it? He sighed and dropped his head down on the desk, feeling angry and disgusted with himself. Snape's right about me, he thought bitterly, I might as well be supporting the man for all the good I've done here. Can't even open my mouth and tell Dumbledore the truth.

He groaned. Stupid, stupid, stupid. Why had he ever trusted the man? I was young, he thought immediately, We were all young. I was a werewolf. I would have trusted anyone who wasn't cruel to me. It wasn't my fault! He had repeated these words to himself every day for the last thirteen years, and he still didn't believe them.

Every time he gathered his courage to tell Dumbledore about Siriu--Black's Animagus form, the words died on his lips. Why couldn't he do it? Why was he such a coward? Black had betrayed him. He had betrayed Lily and James. If anyone deserved to be in Azkaban, to have his soul sucked out, it was him.

And yet, Remus' traitorous mind protested, as it did every time, Black had kept his secret. All those years in Hogwarts and beyond, and no one had every known. Except Snape, he reminded himself. And look where that had got him - but he knew it was a feeble argument. It had been reckless and immature, but it hadn't cost Remus his life or his freedom. Of course Snape hated him now, but then, Remus thought with a resigned smile, he always had.

Black had kept his secret, Remus thought again. Ever since that night in the Shack, he had never said a word. Couldn't he do the same?

And yet...every time he looked into Harry's green eyes and saw his messy hair, he saw Lily and James looking back at him reproachfully. The boy's parents ahd died betrayed by their best friend. It had worked out for the best, in the end, with Voldemort's defeat, but no one deserved that kind of death, and Harry didn't deserve the life he lived as a result. Black had betrayed Harry's parents. He deserved justice. Was Remus not just as guilty for withholding information that would bring it to him?

He could push all these feelings down if it wasn't for Harry. The boy's haunted green eyes seemed to stared at him at every turn. Remus knew when he looked into them that everything was his fault. He had trusted Black, and because he and Lily and James had been so foolish, Harry had seen things that most wizards died facing. Remus shuddered to think what memories the Dementors brought him - the boy had fainted on the train, and he could only imagine why. He had been afraid to let Harry fight the boggart - the horrors in Harry's memory were not the sort of thing he wanted appearing in the classroom. Children afraid of banshees and spiders would not react well to Lord Voldemort's appearance in the classroom.

Not that anyone else would, Remus thought grimly. And he and his friends hadn't exactly had any more terrifying fears, he thought, and couldn't suppress a grin at the thought. That memory was fresh in his mind today, and for good reason. He had taken half his speech to the third years from it. It had been in his own third year, on the third day of term...

The third year class filed into the classroom, chattering happily. Most of the conversation was wondering what this year's classes would be like. Their professor had been away during their second year, and the substitute hadn't been very good. Their first year, their professor had thought to teach them the basics first, but this year he had promised more action. The class was currently engaged in wondering what exactly he had planned for them.

Four students, however, were uninterested in this line of talk. "Remus," James was saying, "Where were you last night? It was only the second night! Your mother can't be sick already!"

Remus was pale, and there were dark shadows under his eyes as if he had been up all night, but his voice was steady as he answered. "No, I had a slight cold," he said smoothly, "I had to go to the Hospital Wing. Madam Pomfrey kept me overnight and made me eat breakfast in the Hospital Wing. She wouldn't let me go until the second bell."

Sirius gave him a sharp look. "You didn't have a runny nose yesterday in class."

Remus flushed. Why did his friends have to be so observant? He was about to answer, but James unwittingly came to his rescue. "He looked tired, though," the other boy pointed out, "Not as bad as he does now, but he kept falling asleep at dinner, remember?"

"That's true..." Sirius said, but he gave Remus a suspicious look that made the other boy swallow nervously and hope he wasn't turning too red.

"You're so lucky you missed class," Peter said enviously.

Sirius gave a bark of laughter. "Remus? Miss class? He probably went mad!"

Remus smiled. "I was afraid she'd keep me all day."

"Typical," Sirius muttered. "I'd have given anything to be sick through that Potions class we just had. Miserable!"

"Slughorn hasn't gotten any better, huh?" Remus said with a small smile.

"Oy," Sirius replied gloomily, "Man just wouldn't shut up. Kept going on about how smart Evans is, and wouldn't shut it about Snape either. Greasy bastard couldn't keep the smug look off his slimy face. Like to break his big fat nose," he added moodily.

Peter looked at him nervously. "You'll get expelled for sure!" He protested.

"S'bound to happen anyway, according to McGonagall," Sirius said, "Might as well be for a good reason."

Remus wasn't sure what to say to this pessimistic statement, but luckily James always knew the proper response to Sirius' gloominess. "Don't worry, mate, we'll take care of him. I've got...ideas for this year."

Sirius brightened. "Good. Let's talk after class."

"Did he even do anything to you?" Remus asked, but they didn't notice. He sighed. "What about your other classes?" He said, changing the subject. "What happened yesterday?"

"Divination," James groaned.

"Professor Silvasky is nutters," Peter said, "We shouldn't have signed up for that class."

"You're just saying that because she said you were going to die," James told him.

"Lucky we didn't take it, Remus," Sirius said with a grin. "Of course, James only took it so he could be with Lily."

"Shut it, Sirius," James said easily. "He's right though, Remus...you're lucky you didn't take that class. It's a nightmare."

"You'll give me your Potions notes, though, won't you?" Remus said anxiously.

"Of course, Professor Lupin, don't be so crabby," Sirius said lightly. "Anyway, Remus would die before he missed a Defense Against the Dark Arts lesson. It would be like James missing Transfiguration."

"Shut it, Sirius," James said again, "Anyway, I wouldn't want to miss Defense either. It's supposed to be more fun your third year..."

"Wait, aren't we missing something?" Peter said suddenly.

The four boys looked around.

"Yeah," James said finally, "We're supposed to have a teacher."

The other three blinked at him. "So we are," said Remus, "Where is he, anyway?"

By now the rest of the class had realized that they were alone in the room. They had taken out their books, parchment and quills, and were now wondering loudly what could have happened to their professor. Sirius was describing in great detail all the gruesome deaths he could have fallen to when the door opened and their teacher walked in, looking slightly frazzled.

"I have a special treat for you today!" He said in his great, booming voice, "I know you all have been looking forward to meeting some deadly monsters, so I thought I'd find a dangerous creature for you to gruesomely vanquish. Put away your books, take out your wands, and come with me!"

The class did so, exchanging nervous, and, in the case of Sirius and James, excited looks. "A practical Defense class!" Sirius was saying excitedly as they walked down the hall, "I can't wait to see what we're fighting!"

"I hope it's not anything too dangerous," said Peter, who had turned whiter and whiter at each word of his teacher's speech. "You don't think he would give us anything that could kill us, do you?"

"Peter! Lighten up, it'll be fun!" Sirius said impatiently. Peter didn't look convinced.

"Professor Greenbriar wouldn't give us anything too dangerous, Pete," James said repressively, "Just relax, all right? You're not going to die."

"Okay..." said Peter, but he still looked a little green.

They followed Professor Greenbriar around a corner and into...a dead end. There was nothing in the hallway but a large grandfather clock standing up against the wall. It seemed to be chiming a lot more than usual...and a closer look revealed that it was shaking a little bit.

"Here we are, class!" Professor Greenbriar said cheerfully, standing in front of the clock and beaming at them. "Gather round, gather round! Don't be too nervous!" he added to the people who were eyeing the clock apprehensively, "There's a boggart in there! A terrifying creature, yes, but I'm confident any deaths today won't be too ghastly!"

This did not seem to calm anyone down - most people looked even more frightened than they had been before, and Peter was shaking with terror.

Not everyone looked scared, though - James and Sirius looked positively delighted, and their Muggleborn classmate Lily Evans, only looked mildly interested. She probably hadn't heard all the horror stories about boggarts, Remus decided.

"Now, before we let the boggart out, let's talk a little bit about them," Professor Greenbriar said, getting ready to lecture.

"Most boggarts like enclosed spaces - the space underneath beds, wardrobes, cupboards - I've never seen one in a grandfather clock before, but apparently the Headmaster realized there was something in it when the hands on the clock started going round and round for no reason." He beamed at them. "I asked him if I could use it for a lesson with my new third years! I thought it would be an interesting first lesson. Aren't you glad we're done taking notes?"

The class gave a weak chuckle, but most people were still eyeing the clock apprehensively. Their professor gave them a short lecture on the properties of boggarts and how to banish them, and then they got down to business.

"Now, would anyone like to assist me?"

James' and Sirius' hands shot up instantly, but Professor Greenbriar was looking thoughtful. "No...how about you, Mr. Pettigrew?"

Peter gave a small squeak, and James and Sirius put their hands down, looking disappointed. "Um...me, Professor?"

"Yes of course, Mr. Pettigrew, you'll be perfect for this," Professor Greenbriar said briskly, "Come up here with me, please. Thank you. Now, first things first. What is the one thing that frightens you the most?"

Peter gave a terrified glance to the rest of the class, but they were all watching him with interest and had no help for him, so he was forced to look back into the cheerful red face of the professor. "Well...there are a lot of things, Professor," he said honestly. The class laughed.

"There has to be one thing, Mr. Pettigrew, that scares you the most, can you think of what it is? You can take a minute," the professor said kindly.

"Um...actually, I'm rather scared of rats," Peter squeaked nervously, and privately Remus thought he sounded rather like a rat himself.

"Okay, so when the boggart sees you, it will turn into a rat. Now don't be alarmed, Mr. Pettigrew, but it will probably turn into a rather large rat, possibly with red eyes and sharp teeth and a foaming mouth. Now, Mr. Pettigrew, don't squeak, you'll manage. The way to vanquish a boggart is laughter - to force it into a shape that makes it amusing. So to vanquish your rat, you will have to make it funny. Can you think of a way to make it funny, Mr. Pettigrew?"

"Put it in a dress," Sirius said promptly.

"What is it with you and putting things in dresses?" James said under his breath (but loudly enough for everyone to hear, of course). "Let's put Snape in a dress, let's put the school owls in dresses, let's turn Malfoy's robes into a dress..."

The class laughed, and Peter grinned weakly. Professor Greenbriar was holding back a smile. "Thank you Mr. Potter, that's enough. So what'll it be, Mr. Pettigrew?"

"I'll...put it in a dress," Peter said.

"What kind of dress?" the professor prompted.

Peter gulped. "I...I don't..."

"Pink," Sirius whispered to him.

"Pink," Peter repeated firmly.

Professor Greenbriar looked disappointed, for some reason. "You don't have any ideas of your own? No additions?"

Peter stared at him in confusion. "What?"

"Never mind," he said impatiently, "Anything else?"

"Polka dots," said James under his breath, and Peter repeated this suggestion dutifully.

Professor Greenbriar sighed. "All right. And how about a big pink bow on the tail?"

"Okay," Peter agreed.

The class was giggling now, and the clock was chiming louder than ever. "Can you picture that in your mind's eye, Mr. Pettigrew? Get a clear image of that rat, and when you point your wand at the boggart and say Riddikulus, it should be forced into that dress."

"Yes, sir."

"Now, I want the rest of you to decide what you are the most afraid of and how you can make it amusing. I'll give you a moment to think."

The hallway was quiet as people thought. Remus didn't even have to decide what he was afraid of - he knew it had to be the full moon. But how could he make it funny? It turned him into a bloody monster every month, how could he laugh at it? Maybe if he blew it up right out of the sky...he grinned. Yeah, that would be cool. Like breaking a glass ball...

"Time's up!" said Professor Greenbriar cheerfully. "Hope you're ready to face your fears!" And with that, he pointed his wand at the clock's door and made it fly open. "Pettigrew! Go!"

The class screamed as a giant rat came scuttling out of the door, evil and foaming at the mouth. Peter froze.

"PETTIGREW! GO!" Professor Greenbriar yelled.

"Peter! Do it!" James, Sirius and Remus urged him.

"R-R-Riddikulus!" Peter stammered finally, and the whlole class burst out laughing as the rat rose up on its hind feet, wearing a little pink dress.

"Smith! Forward!" Professor Greenbriar yelled when the boggart froze, confused.

One of their classmates rushed forward. The next few minutes were a blur as people vanquished zombies, mummies, banshees and Lethifolds. Then...

"LUPIN! Forward!"

Remus' blood froze. It was just as bad as he had feared. The full moon shone ominously above his head, a symbol of everything he hated and feared about himself. "Riddikulus!"

There was a shattering sound as the moon broke into a thousand pieces all over the ground. Remus felt a wave of satisfaction, and he laughed out loud with glee. He barely even noticed that the rest of the class was silent and staring at him in confusion.

"Very good, Lupin. Potter! Black! Stop staring!"

But James and Sirius hadn't been paying attention, and when they heard their names they both ran up at once. The boggart became bewildered, and they didn't even have to say the incantation because it became...half a slug?

There was a wave of confused laughter. There was a series of cracks as the boggart switched from a severed hand, a spider, and a rattlesnake.

"Very good, class, you've confused it! Pettigrew! Come here and finish it off!"

Peter rushed forward and waved his wand. Remus got a faint glimpse of a pink dress before the boggart disappeared in a wisp of smoke.

"Excellent, class! Excellent! Potter, Black, what happened with you?"

"We got confused, Professor," said James, who was rather red in the face.

"Not to worry, Potter, not to worry. What was your worst fear?"

James exchanged glances with Sirius. "A headless corpse, sir."

"And you, Mr. Black?"

"Flesh-eating slugs."

"Ah! Well, it all makes sense now. You see, you confused it by advancing at the same time. It wasn't sure what it should have become, and so it was not at all frightening. That was fantastic, boys, ten points to Gryffindor. And I think five to everyone who vanquished the boggart, and of course ten to Mr. Pettigrew - you did it twice. That was wonderful, class, thank you very much. You are dismissed."

The class turned and left the hallway, chattering excitedly.

"Half a slug! That was so COOL!" Sirius glowed.

"Did you see the rat?" Peter said happily.

"Yeah, that was cool, Peter," James said with a grin. "I'm glad I didn't have to see a headless corpse!"

"Lucky you," Remus said, but he wasn't smiling.

"What's wrong, Remus?" Sirius said.

"Yeah...why are you afraid of crystal balls?" Peter asked.

"I think that Divination class went to your head," Sirius said. "I thought it was a--"

"It's a long story," Remus interrupted, "I'll tell you sometime. Let's just go to lunch, I'm starved."

The others made loud agreements and sped up down the hall, but Remus wasn't sure his distraction worked on Sirius - he was still giving him suspicious looks all the way through lunch.