Professor Lupin grabbed a piece of chalk from a cut-glass bowl on his desk. He had only managed to write the letter "T" on the board before a loud honk echoed through the room, sounding like an entire flock of geese had blown their noses simultaneously. He turned around and surveyed the room. Most of his fifth years were stifling giggles, or openly smirking. Though he had grown to know and respect the Weasley boys' reputation for pranking, it would be premature to make accusations. He merely raised his eyebrows and said lightly, "I suppose I am not the only one getting over a cold, then."

The class laughed. Lupin turned back to the board and wrote "The Legal Ramifications of Unforgiveable Curses." A symphony of honks, some as high-pitched as a pixie's voice and some low, like a troll's, issued as he traced each letter. Lupin stepped back and eyed the chalk in his hand. An idea occurred to him. "Clever..." he murmured, hearing several giggles behind him. He wrote the letter 'a' three times in a row on the board. Three identical high-pitched tones sounded. He wrote 'z' and heard a deep, bellowing honk. Lupin smiled. He turned to face the class.

"I see we have a bit of a joker with a taste for music," he said. "I don't think any of you are in Professor Flitwick's choir, though, are you?" The Slytherins rolled their eyes and several Gryffindors laughed.

"Nobody outside of Ravenclaw does that lame stuff," sighed a Gryffindor girl with pale, milky skin. Lupin had to glance at his seating plan to remember her name—Etain. He didn't recognize her surname; she could not have been a pureblood.

Lupin returned to the chalkboard. He paused, thinking back to his mother, her messy braids, the painted china lamp that looked like a rocket ship in the house back in Suffolk, back Before. She used to sing to him when she tucked him in at night and he would join along, making her laugh with his unintentional malapropisms, his voice bright and squeaky. Lupin wrote a sequence of letters on the board, and they sang out a well-known melody, a wizarding lullaby almost anyone in the class would know. His dad had taught his mam that one before he was born.

"That's wicked," said one Weasley twin.

"How'd you know how to do that off the top of your head?" asked the other, sounding genuinely impressed.

"They're just musical notes," said Silvanius Nott, sounding bored. "Each one's a half-tone apart, like on a piano."

"Silvanius is correct," said Professor Lupin with a gracious smile. "But I wonder who will take credit for this artistic intervention into our OWL preparations today." The classroom went silent for a moment, though quite a few students twitched. "Alright, then, the artist wishes to remain anonymous. In that case, we will continue with our discussion of the Unforgiveable Curses." He strode over to his desk and rummaged around in a drawer for the fifth year textbook‑ Nox: Practical and Philosophical Investigations into Dark Magic and its Defenses. Page 135 was bookmarked with a quill. He scanned down to the paragraph he wanted to quote and then tapped the chalkboard with his wand, muttering "Scourgify." Professor Lupin tapped the board again; the text appeared, quite a bit messier than his handwriting, but it would have to do, otherwise the whole period would be lost to honking and giggling. They were already behind because of him; then Snape had to come in and teach a completely irrelevant lesson, confuse all the fifth-years as to what their homework was and try to out him as a werewolf all in one go. You had to give him points, thought Lupin, for hitting several birds with one stone.

"The Unforgiveable Curses," he said loudly, gathering the class's attention. "Who can tell me what they are?"

A jumble of voices responded, talking over each other, some listing the names of the curses, others the incantations and yet others what each curse did.

"Yes, yes, that is a list of the curses, which I believe you are meant to have covered in your fourth year—but who can tell me what all the curses, considered together, are?"

"Unforgiveable, I'd reckon," said Fred Weasley, who was sitting in George's spot on the seating plan. Lupin had not yet divulged that he could easily tell them apart; it would be difficult to explain.

"They're dark magic," said Melissa Yaxley, a Slytherin. "They're illegal."

"All correct answers," said Professor Lupin, sounding amused, "but not quite what I was looking for. What I mean to ask—and there is no hard and fast answer to this question—is this: why are these particular curses unforgiveable? What does casting an Unforgiveable do to the soul of the wizard who casts it?"

He paced back and forth around the front of the classroom, rolling his wand between his fingers. There were quite a few more Slytherins than Gryffindors in this year. Then again, though Lupin, when you considered that all these kids would have been born during the height of the war, it made sense, given who their parents were. They were fifteen—born in '78 or so. The year he had finally passed his Apparition test, joined the Order of the Phoenix, been interrogated by Ministry bureaucrats for information he could not give.

"Well," he said, pausing at the blackboard, half-formed thoughts weaving themselves into coherence in his mind. "The soul—the human soul, at least, is not a solid, stable thing. You've read Anthea Aarons' treatise on deep magic theory in History of Magic, have you not?"

The professor was greeted with mumbled agreements that assured him that he was correct in having assumed that Aarons was on the history syllabus, and also correct that nobody had actually read her.

"If you don't remember, Aarons explored the deepest and most profound magics in her famous experimentation, conducted during her travels in the Middle East," he said, and tapped the board with his wand so that notes appeared. "She established that the soul was a mutable, changeable organ—more akin to jello than to stone."

"Is that why your heart feels so wobbly when you see me?" snickered Lee Jordan to a pretty brunette girl, who half-heartedly levitated her textbook over to smack him in the head.

"Yes, yes, it might have been a poor analogy," said Lupin, "but the point is, the casting of an Unforgiveable Curse not only requires a certain level of toxic hatred on the part of the caster, but it also reflects back on the caster some essence of the spell that he or she has just performed."

Herbert Goyle scrunched up his face and said, "I don't get it."

"Take the Imperius Curse, for example." Lupin deliberately chose what seemed like the least horrifying of the three curses. "Casting the Imperius Curse removes the autonomy of the victim, leaving them with little to no free will. The wizard or witch who casts it, however, maintains power over both themself and their victim. But successful casting of the Imperius Curse is usually attributed to wizards who are unable to control their own base urges—in this case for power, domination." He realized he'd lost Goyle during the first sentence, but the rest of the class seemed to have leaned forward, their attention caught.

"Continuing on with our example of the Imperius Curse, maintaining a hold on the curse's subject requires extreme concentration. It is hard enough to steer one's own life without having to perceive and direct somebody else's as well. Perhaps some of you might imagine trying to keep up with more than one class at the same time," he said.

"I can hardly keep up with one class at a time, and there's two of me," observed George. Fred nodded in agreement.

Professor Lupin smiled as Fred winked at a girl with tightly braided cornrows. "Yes, of the three Unforgivables, the Imperius is known as the most mentally taxing. Wizards who must maintain control over their subject's behaviour often experience lapses in concentration in their own life, as well as difficulty with cognition, slower response times, inattention to detail and forgetfulness."

"I wonder if Longbottom's not as thick as he seems," drawled Silvanius Nott.

Lupin tensed. The image bloomed in his mind, unbidden. Alice in the wheelchair, the spit dripping down her chin, her hands folded weirdly in her lap. Frank sucking on his wand like a dummy, crying out when he burned his tongue. Lupin opened his mouth to retort, but nothing came out. He closed it and turned away from the students to the blackboard.

"Some of these effects," he continued, "last even after the Imperius Curse is lifted. Particularly when the subject is kept geographically distant from the caster, or when the Curse is maintained for a long time, the wizard or witch who casts the Imperius Curse can be left with permanent cognitive damage, which affects the wizard's ability to make choices on their own behalf." The cursive letters unfurled in chalk before him at the touch of his wand. "So you see, the core effect of this particular curse—the removal of autonomy, of free will—this is something which reflects back on the curse's caster."

He turned to face the class. The kids were all staring up at him, some with awe, others with the pinched expression of either incomprehension or bowel troubles.

"Do you understand?" he asked simply.

Angelina shifted slowly in her seat, leaning her cheek onto an upturned hand. "So you're saying...the curse kind of backfires..." she mused.

Lupin smiled. "Yes and no. A curse—well, a curse can backfire literally, yes, in some cases." A backfiring Unforgivable curse. There was only one example he could think of, and he pushed it out of his mind. "But what I'm talking about is how casting a brutal curse affects the soul, or rather, how damaged a soul must first be in order to cast an Unforgivable. It's something of a closed loop, a, a...a circle of destruction. This type of dark magic—it circumvents the laws of the heart, as Aarons put it. It exists outside of time."

"But that isn't the curse affecting the soul, it's the soul affecting the curse," interrupted Melissa Yaxley. "So, you can't say casting an Unforgivable really does anything to your soul. I mean, whether or not you get, I don't know, brain damage, and that's pretty rare, isn't it?"

Lupin exhaled and ran a hand through his thinning hair. He knew what he meant, what thoughts clung to the inside of the mind, but whether or not he could articulate them to a class of fifteen-year-olds...kids who had grown up safe, who had never made impossible choices, who were never forced to cast a spell that had left them nauseated, sweaty and disoriented in a public toilet far from home. Wherever that was. He thought of giving up, letting the class practice their shield charms and disabling jinxes. He didn't need to force them to think critically about Defense. Lord knows it wasn't on the curriculum and since when were Hogwarts professors really evaluated on their performance, anyways? His predecessors certainly weren't.

Instead, he gently said, "It's something of a paradox. I know it must seem unfathomable, especially at your age." That was the wrong thing to say and he knew it even as he said it aloud and eyes rolled. He would have rolled his own eyes at their age. He probably had.

"The dark arts...well, as you know, they are not a medium of magic, the way that charms or potions are. They're merely a classification based on intent..." Lupin started again, uncertainly. Where was he going with his? The students looked skeptical. "Part of what makes a form of magic dark is how inseparable its intended usage is from its successful practise. The Unforgiveable Curses, then, are not just unforgivable by the vast majority of wizarding society, or by the law. They are unforgivable by the soul itself, which may not recover from its abuse by the wizard's, er, shall we say, conscious mind."

The class stared at him. He had lost their interest; he knew it now. Placing his wand down on his desk, Lupin noted the sticky fingerprints and dirty glaze coating the hand-grip. He would have to clean it later. Lupin disliked allowing his possessions to become damaged or unclean; it was much easier to take care of them then find the money to have them replaced.

"Professor?" It was a Slytherin, Ptolemy or something, the boy with dark brown hair and a cold, closed expression. "Do we have to know this for OWLs and the midterm?" He was twiddling his quill between his index and middle fingers, the way Padf—the way Black used to, when he was impatient in class.

"I wouldn't expect this to show up on OWL exams," Professor Lupin said gently, "but any material we cover in class is fair game for the test." At the class's communal sigh, he added, "But, as deep magic theory is technically a subjective field, unlike spellwork, I will accept a range of interpretations on the ramifications of Unforgivable curses, as long as you show some reference to the source text in Nox. The students looked somewhat mollified by this, so he sat down at the desk and slipped his reading glasses on.

"I'd like you to get into groups—not yet, Mr. and Mr. Weasley, but when I am finished speaking—and discuss the reading I assigned last class and how it relates to our discussion today. Feel free to agree or disagree with Icarus Pennants," he added. "This is an exercise in your ability to interpret magical law as it relates to the dark arts." Lupin flipped through the textbook, finding the stack of papers for marking that he had tucked between its musty pages. "Your homework today will be to write a short response to the discussions you have had with your groups. Any questions?"

The children erupted into a flurry of noise. One student leaned forward across their desk abruptly and knocked over an inkwell onto the satchel of the student in front of her, while a Gryffindor and a Slytherin asked at the same time, "How many to a group?" then turned to each other and yelled "JINX! DOUBLE JINX!"

" 'Ow many inches do we 'ave to write?" whined Charlesworth, a scrawny Slytherin boy with matted blond hair.

"TRIPLE JINX!"

"Two to a group and nine to ten inches should be fine," said Professor Lupin, "although I'd advise you to make your point as clearly and concisely as possible. I will not take marks for a slightly shorter paper that—"

"—QUADRUPLE JINX—"

"—is not short on content. Brevity is the soul of wit, as they say," he added, giving the Weasley boys a sly grin. Both boys—or whichever one of them was responsible for doing the Defense homework (Lupin was not naive enough to believe that they hadn't worked out some more efficient system of getting schoolwork done) had been known to blow out essays into multiple pages by rephrasing the first paragraph over and over again in increasingly metaphorical terms.

"—MERLIN WINKS, SNOG A SPHYNX, SAY THE RHYME OR YOUR MUM—"

Lupin silenced them gently with a flick of his wand. "That will be enough, Lee, Marcus," he said. They protested silently, their mouths yelling wordlessly in tandem. "No need to worry, I respect the Laws of Jinx. You may both resolve this problem via silent thumb wrestle. Best two out of three. I will referee. The rest of you may get into your groups and start discussing the reading." He lifted the silencing spell.

"Wow. I didn't know teachers understood about the Laws of Jinx," said Lee, sounding impressed. He leaned back in his seat, letting go of the desk in front of him to balance on the two back legs of his chair like a circus performer.

"Oh, teachers understand the rules," Lupin replied airily, "we're just not obligated to abide by them anymore." Alicia Spinnet laughed, while Ptolemy sighed loudly with boredom.

The rest of the class passed by fairly quickly. The kids were well-behaved, having been suitably entertained by Lee and Marcus's thumb war (Marcus won, having thumbs nearly three times as thick as Lee's, and wrists ribboned with muscle.) There were techniques to classroom management that were counter-intuitive, thought Lupin. Some teachers could command respect and obedience with strict rules and sharp glares. Others, like Filius Flitwick, ceded nearly all control of their class and gave in to controlled chaos, trusting in his students to practise their spellwork out of interest or enjoyment. Though Lupin wasn't old enough to have seen Dumbledore teach, he'd heard from others that Flitwick most resembled Dumbledore in his teaching methods, which seemed about right. He couldn't imagine the serene, good-humoured old man shouting over the laughter of children or assigning detentions for students having a chit chat.

He didn't have that luxury. The kids were used to seeing their Defense professors come and ago like grammar school substitutes, and expected to be able to bully or outright ignore them into submission. Professor McGonagall had warned him as much. Aware of his shabby appearance, his fatigue and physical limitations, Lupin knew that his approach to the job would have to be much more proactive if he hoped of exerting any authority over his students. And unlike Severus, thought Lupin with some mixture of amusement and contempt, he preferred not to use humiliation as a means of asserting his dominance in the classroom hierarchy.

Lupin was not authoritarian by nature and had a long history of negative experiences with the figures who held the short reins of his life in clenched fists, loosening or tightening their hold on his autonomy for arbitrary reasons he was never privy to. Assigning a student detention, or some other form of punishment—even if it was well-deserved—tended to make him freeze up with self-doubt. He preferred to prevent the need to discipline any students in the first place, using a combination of passive tolerance of minor transgressions and the wry sense of humour he had honed from a young age.

The noise level remained fairly steady in the class as the students (hopefully) discussed their reading and Lupin graded the papers he had tucked into his textbook. At one point, Lupin heard the soft whistle of an enchanted paper airplane soaring directly towards him and, without looking up, he knocked it out of the air with a quick brush of his wand. The Weasley twins—that was their style. More slapstick than artistic. They were good at what they did, but it was fairly juvenile humour, much less sophisticated in concept than the sort of pranks he had pulled with his friends, back in the day. In execution, they were flawless, though. James and Sirius hadn't achieved quite the same level of effortlessness in their hijinks until well into their sixth year. Now, the musical chalk had been elegant and perfectly executed. In fact, he couldn't even guess who had come up with it. Whoever did it had obviously checked the Defense schedule to ensure that nobody would be in the classroom for enough time beforehand to charm the chalk without detection. Not only that, but if they were in Lupin's fifth-year Slytherin and Gryffindor class, they were maintaining a perfectly straight face.

Lupin wrote a final comment onto a second year's essay in neat cursive and tucked the papers back into his textbook. He glanced at his watch.

"Our class is done for today," he said. The class had already gotten up. Some students were shoving corked inkwells into their satchels while several others lingered in the doorway impatiently. "Please remember to write the response papers for your partnered discussions," added Professor Lupin, raising his voice above the growing din. "I will give extra marks for referencing the assigned readings from last—oh, hello, Fred," he said sheepishly to the redheaded boy leaning across his desk. "I've lost my audience already. Can I help you with something?"

"I'm actually George."

"Alright then, George," said Lupin, a slight smile creasing the corners of his eyes. "How can I help you?"

"Well—it's actually about Mr. Filch—the caretaker?"

"Yes..."

"Well, see, my brother and I found out it's his birthday coming up next Friday, you know, and we thought—"

"You thought you might give him a surprise." Lupin repressed a smirk. "That's, er...thoughtful of you."

"You know, Fred and me think he's probably our favourite staff member at Hogwarts," said the boy with a grin. "No offence to you or McGoogles," (at this Lupin's mouth twitched open and closed), "I mean McGonagall, but the amount of quality time we spend with Mr. Filch...it's a relationship we treasure. Strictly professional, though, of course."

"And you wanted next Friday off...?" He sighed. "I'm afraid I can't do that, Mr. Weasley."

"Oh no, not at all, Professor," Weasley backtracked. "Me and Fred would never miss an academic commitment voluntarily—well, except if its Binns' class, but I suppose you'd understand, seeing as he probably taught you too...?"

Professor Lupin chuckled. "Yes, I'm not quite that old."

"Oh, we know how old you are," Weasley assured him boastfully. "Thirty-three, isn't it?"

Lupin raised an eyebrow inquisitively.

"We didn't look it up, you know. G—My brother and I found your name in some...documents of purely historic interest."

At this, Lupin blanched somewhat. Was it...did it have to do with—

"We were doing a bit of research on behalf of old Argus's special day, you know, trying to find out exactly what kind of surprise he'd most appreciate, and we found a few gems in the old detention records. Really interesting stuff," Weasley added, seeming to smirk at Lupin's reaction. The light filtering through stained-glass windows outlined the boy's freckled nose in bluish-green. Beneath the long nose was an easy grin, just this side of smug. The expression was pure James, all winking candor and lopsided grace.

"I see," said Lupin impenetrably. "And has your opinion of me as a teacher been so terribly undermined by your findings?"

"Of course. My apologies, sir, but I don't think I'll quite be able to respect the authority of a person whom I know to have been sighted atop Gryffindor Tower, standing on one foot, wearing only Professor McGonagall's tartan bathing suit and shooting porridge out of his wand at every passing raven whilst singing "My Beaters Lie Over the Ocean."

Lupin gave a curt smile. "I lost a bet." Something twinged down in his throat, painful but cathartic, as though a knot inside him had been untied to allow fresh air into his old lungs. It ached. It tingled.

Then Weasley winked, and the ache disappeared. "Alright, Professor, here's the question. You tell us how you got Filch's dad's address for the trick with the exotic dancing centaurs and we forget about everything we found in the detention files. Everything," he emphasized sharply.

"Absolutely not." Even as he said it, it occurred to Lupin just whose name might have come upon alongside his in some of those files. But he could not afford to lose this job—and if they asked, he could fudge—but, then again...

"But, Professor! You wouldn't be helping us. You're just telling us, in theory, how to trace—"

"Mr. Weasley," Lupin cut him off with a gentle shake of his head. "As your teacher, and as an employee of Hogwarts...this is not something I can know about."

"It's just a piece of information. It's not like we're going to, you know, pull the same prank as you did—though, nice job, by the way. We can't repeat a prank, it's against—"

"The Hellion's Prescript. Oh yes," he added as Weasley raised his ginger eyebrows, "that thing's been around for ages." Which was true, if you looked at it from a fifteen-year-old's perspective. "Now, I understand you and your brother have an, er, a tradition to uphold. And I realize there is not much I can do to stop you which hasn't already been unsuccessfully attempted by your Head of House."

"Oh, she's tried everything," he tossed off haughtily.

"Which is why," said Lupin, as he gathered his papers and tucked them into his briefcase neatly, "I will give you a favour and a warning. It is possible, though quite labour-intensive, to look through the Ministry's old records of registered wizarding households in Britain to find the address of any given registered household, though I cannot promise the archives in the Hogwarts library are up to date. This information is technically publically available and I am not prohibited from sharing it with you. However," and at this he snapped the clasps of his case shut for emphasis, "as your teacher, if I am the one to catch you engaging in any, er, lawbreaking or otherwise taboo behaviours, I'll have no choice but to...well, give you detentions, I suppose. I don't think they allow the sorts of punishments here anymore they used to give, back when I was here." He allowed himself a moment of fond reminiscience. Peter had been subjected to three hours of the tickling hex in the dungeon...poor old Peter.

Weasley bowed. "Thank you, Professor. I knew you'd come through." He slung his canvas bag hover his shoulders and made to leave the classroom.

"Wait!" called Lupin. Weasley paused in the doorway. "I did not support or in any way encourage what may or may not transpire on Friday," he said strongly.

"No, of course not."

"And I would appreciate it if that little anecdote about Gryffindor Tower did not...well, leave our confidences."

"I have no idea what you're even referring to."

Lupin nodded at him. "Thank you. Fred."

He tapped his wand on the blackboard in several places, trying to get a sense of the charm used for the musical prank. Weasley had already stepped out the arched, oaken doors when he paused and spun around.

"Wait. How'd you know—?" he asked, tentatively.

Professor Lupin stepped towards him. His facial expression was unreadable as a sphinx, one hand clutching lightly as his threadbare tie. "As your Defense Against the Dark Arts teacher, " he said, "I will tell you that it is important and useful to learn...to differentiate between people who, at first, seem as though they are...the same."