TUNNEL

The Express had already commenced its gentle rocking as it gathered speed, the whistle having blown and the clickety-clack well underway, and Snape made unsteady progress down the vestibule in search of an empty compartment.

"Back in your seats!" he barked at random students he encountered, indifferent to their wide eyes of surprise at this unexpected passenger in their midst. This was the first time Snape had caught the Express to Hogwarts in over a decade. It was not to his liking, and in full glower and black winter cloak, he brooked no argument, and anyone other than a prefect or senior scrambled for safety in a nearby compartment, whether it was theirs or not.

Through the windows, the grey blur of London outskirts flashed by, but the good citizens and visitors of that town paid the train no mind – an abundance of concealment charms dressed down the Express' vibrant livery and turned it into a non-descript passenger train on its way to…somewhere. Muggles lost interest almost immediately. Inside, however, was a tumult of excitable children returning for second term at Hogwarts, having been home for Christmas, and Snape's head was already hurting. He needed peace and quiet.

Almost at the very end of the last car, where the more sedate seventh-years had taken up occupation, Snape at last found what appeared, at a glance through the window of the sliding door, to be an empty compartment and in relief pulled hard on the handle to open it. Then he discovered there was in fact a person within, seated on the padded benchseat with legs crossed and holding a book, who looked up in surprise.

"Lupin -,"

"Severus?"

Snape hesitated. Lupin's expression was at first genuine astonishment, but it hardened a little as they spent a silent moment contemplating each other.

"I'll find another," said Snape shortly, and had begun to draw the door to a close when Lupin spoke.

"Don't be ridiculous. Take the other bench."

Snape paused, glanced at the tempting stretch of empty, fabric-covered seat and then shook his head. "I think not."

Lupin shrugged one shoulder and turned his attention back to his book. "There aren't any others. Not unless you fancy toxic densities of teenage hormones, sticky sweet wrappers and several hours of eye-rolling, adolescent gossip. I understand there's a toad loose somewhere."

Snape frowned and lingered a moment. The description was extremely off-putting.

"I intend to nap most of the way," Lupin added, a brow raised, and he looked at Snape over the top of his book.

"Fine," muttered Snape and threw open the door again, entered and slammed it shut behind him in one openly irritated movement. He tossed his hold-all onto the seat directly opposite Lupin, removed his cloak and threw that over the top of his bag, then stiffly assumed position in the seat nearest the door, folding both his arms and legs.

Lupin coughed, turned a page and then there was quiet for a full two minutes.

Snape was a little surprised. He had presumed Lupin would initiate a conversation, being of the gregarious type, unable to bear the discomfort of silence. But no words were spoken and, encouraged, Snape reached over to his bag and pulled out some reading material of his own: some journals and yesterday's paper – perfect for placing over his face should he find himself nodding off as well.

The rhythmic chunting and rocking of the train, the blur of scenery outside and the quiet soon had Snape reading the same passage repeatedly as he fought drowsiness. His nights in the hospital ward had not be conducive to sleep, and fatigue was stealing up on him now. When he discreetly glanced over at Lupin, the other had his book held up too high to tell whether he was faring better, but the occasional rasp of a page being turned seemed to suggest that reading was happening in earnest. Snape wondered what it could be that was so stimulating – the blank cover told him nothing.

Unexpectedly, Lupin lowered the book and Snape glanced away, but too late. Lupin smiled. "Just a bit of background on Patronuses," he offered, giving the book a little waggle. "Picked it up at Obscurus. I'm afraid it hasn't told me anything I don't already know."

"Oh?" grunted Snape. "Bit of an expert?"

"As much as anyone can be."

"For Potter's benefit, I'm assuming?"

"Dumbledore mentioned his extra-curricular training then?" Lupin lowered the book but looked out his window.

"In passing," said Snape, non-committedly. "I know the Board have permitted it. I suppose he wanted to explain why your appointment continues to the end of the school year. Against my advice, of course."

Lupin smiled again, but his gaze remained fixed on the view. "Did he tell you anything else? Out of interest."

"Well it rarely takes long on the subject of you for the name Black to be raised…"

Lupin glanced back. "On the subject of me? So this was just conversational chit-chat over chess or was I item on some agenda?"

Snape raised a brow but didn't respond for a moment. He re-crossed his legs. "If you have concerns about who and why the Headmaster chooses to converse with, perhaps you should take that up with him."

A sigh issued from Lupin and he looked resigned. "Of course. Then you'll know why I was in London."

"Not particularly. Book shopping, evidently. Christmas lights?"

"Ha, ha – a little joke, Severus? In fact, the Ministry have hit me with a bill for just over five thousand Galleons to be repaid. I could give them three, but the rest has been spent. If the total's not recovered within three months, I face time in Azkaban for -,"

"Benefit fraud. Fraud by omission?"

"So you do know."

"I'm not sure why you're telling me this, Lupin. I doubt you'd go to Azkaban for late fees. More likely they'll just confiscate your broom. Or rather, Potter's."

"No need to be glib," retorted Lupin, appearing pained. "I understand you'll be relishing the news but it actually quite serious for me. I suppose I'm…sharing…in hopes you'll take a more…accommodating attitude in future."

Snape snorted, a wry smile rose briefly. "You're asking me to be the better person? Take a moral high ground? I tried that."

"I'm not asking you to be a supercilious git. I'm asking you to ease up on the hunt for Sirius. I don't know where he is, I'm just trying to help Harry and do my job. I need the money; I need this break."

Snape sighed heavily and folded his arms and for a minute neither spoke, their gaze in opposite directions. Students moved up and down the train corridor, occasionally glancing through the window of their carriage and hurriedly moving along at the forbidding scene within.

"What do you mean, Potter's broom?" Lupin then asked, frowning and rubbing a hand down his moustache.

"You're quite sure that's why you weren't in London? Sure you weren't organising an extravagant gift for Gryffindor's number seven?"

"What are you talking about?"

"Don't pretend you don't know."

"No. I don't know."

"The Firebolt. The broom. Ring any bells?"

"What Firebolt?"

"Well I can't help but notice that the amount you need to repay the Ministry is almost the exact amount needed to purchase one of those Firebolt brooms. That Potter just happened to receive for Christmas. Delivered by owl. Was it you?"

"No it wasn't me! Are you saying they don't know who it was from? Wasn't there postage information with the owl?"

"Diagon, obviously. Where else can you purchase a late model broom? Now…who else would have the money to buy one? Perhaps a rich relative…or family friend...?"

"Why not Dumbledore? He's fond enough of Harry. And maybe he did it anonymously so that the favouritism wasn't obvious. It's not as if he hasn't given presents to Harry before…"

"The Headmaster is as mystified as I," Snape responded smartly. "And there's no reason for him to keep that kind of secret from me."

Neither spoke in the time it took for two hedgerow borders to pass. "I'm not sure you're quite as deep in the Headmaster's confidence as you think," murmured Lupin and Snape immediately stiffened.

"Meaning?"

"We'll I wouldn't go assuming that you're that informed about everything. Not everything concerns you."

Snape stewed on this a moment, his brain unable to resist the bait of scanning through all the possible subjects Dumbledore might exclude him from.

"Black," he said. "I'm reasonably certain I know everything I need to know about him. I saw his mangy dog in Hogsmeade. I wonder how he stays warm, Lupin? I wonder what he eats? Or isn't he above raiding rubbish bins in the night?"

Lupin chuckled and toyed with the book in his hands. "How were you so sure it was Sirius? Among all those strays and vermin that follow you around?" He then batted the air around his head, as if swatting at invisible flies.

"Perhaps it was the dull, vacuous expression. Often obtained by persons spending too long staring at the walls of their prison cell. Or motorbike carburetors."

Feigning confidence, Lupin gave another small laugh. Snape's tone had taken on a bitter edge, his mind now idling outside those memories of seventh year. He remembered being last to leave a class, and the Professor stooping to pick up a dropped notebook from the floor. "Whose is this? Do you recognize it?" the Professor had asked Snape, detaining him at the door. Snape had cast his eyes over the doodled drawings on the notebook cover, designs of bikes and brooms, even a Muggle car. Amateurish nonsense, it was apparent within moments of looking that the proportions and scales that these came from the head of someone more fanciful than functional. "Black," he'd uttered, the word coated in contempt. The Professor had then smiled and nodded, appraising the artwork fondly. "Rather good, don't you think?" he'd said, and Snape had almost vomited.

"If you saw his animagus in Hogsmeade," said Lupin, "oughtn't you have brought him to justice? You could have stupefied him easily. Perhaps you were afraid, Severus."

Afraid. Always with this old theme. Lupin looked nothing more than mischievous, rather pleased with himself for having turned the conversation to his advantage. But Snape couldn't help a glower settling, and wrestled to contain it, to override it. "Afraid? We're not sixteen, Lupin."

"I agree. However this conversation is having the effect of bringing it all back. Maybe it's being on the train again. I can almost imagine Sirius and James pulling back the door right now, arms full of goodies from the Honeydukes trolley."

"Merlin forbid."

"I'll be honest, Harry hasn't helped. So like his father. I was starting to move on, and now I've returned to Hogwarts, it's like a time tunnel."

Snape didn't reply. Truth be told, he was experiencing the exact same tidal sense of time drawing back against his ankles, his feet sinking into the sand of memories buried beneath. Dead people resided there, regrets mummified by anger, coffins that should never be opened. He stared out the window in the door. "I thought you were going to nap."

"I never got to ask you. Why are you still here? At Hogwarts, I mean. I heard about the near miss with Azkaban, the war's over…if I were you, I'd've cleared out of the country quick smart. Why hang around somewhere so easily found?"

The Express switched tracks and juddered suddenly. Snape felt Lupin's eyes on him, and he was remembering, even as he spoke, he was remembering being on his knees before Dumbledore. Anything, he'd said. He'd do anything.

"You seem confused, Lupin. You ask as if you'd expect me to answer that. You seem very deluded altogether. On what possible misapprehension did you think I would tell you anything, anything at all, about me or my life?"

The retort hung in the air.

"Because we're grown men, now," replied Lupin quietly. "As you say, we're not sixteen. History notwithstanding…we have different lives now, we're – we're coworkers, we both reside at Hogwarts, there's no reason to hang on to those old resentments. Is there some reason why you can't tell me?"

"I think I made it abundantly clear at the beginning of term. You are here against my advice. You flatter yourself that I still care about…about what happened at sixteen. I have, in fact, moved on. But you are flagrantly colluding with the Headmaster in your appointment, and it is my opinion that an individual with – with your condition, has no place in a school. But I am over-ruled. And to add insult to injury, I am tasked with brewing your infernal wolfsbane." Snape then glared at Lupin. "In fact, had you ever thought about learning to brew it yourself?"

Lupin folded his arms and stared at his shoes. "I'm not allowed to."

"What?"

"It's a rule."

"Seems like a convenient rule, considering you're ignoring all others."

"The Headmaster wanted it this way. He agrees with it, says yours would be as good a guarantee."

Snape silently preened on this, but then Dumbledore had quite calculatedly in the past appealed to Snape's ego to manipulate an outcome, and he suspected this was more at the heart of the matter. But he could accept that Dumbledore would not want to risk the manufacture of the potion. Wolfsbane was one of the most fiendish recipes Snape had brewed, and its maturing requirements were just as fiddly. It didn't store, and the ingredients were always in such high demand, stocks were controlled: one of the reasons Snape was in London. He imagined registered Lycanthropes had their quotas supplied and rationed by St Mungos – so where was Lupin's normal supply while he was at Hogwarts, with a personalised service? If Lupin's appointment was going to be permanent, then some alternative would need to be arranged because he couldn't spend a third of his working day fretting over aconite potency.

"Perhaps wolfsbane can be added to seventh-years potion curriculum. This arrangement is not sustainable," Snape said under his breath. "I'm not a man servant."

Lupin nodded glumly, and then for several minutes the only sound was the clacking of the train wheels and muffled laughter from students in the nearby compartments. Snape sat upright and intractable, shaking open his newspaper in a pointed display of shutting down the conversation, while Lupin flipped his book from one hand to the other and eventually issued a deep, prolonged sigh. When the laughter in the neighbouring compartment rose to a ruckus at that point, Lupin arose and said, "I'll deal with it," then exited the compartment.

While Lupin was gone, Snape found himself growing drowsy again in the quiet compartment. He imagined what he'd be doing now, back at the castle, if he'd been able to Disapparate. He longed to lie down and place the paper over his face but felt that would make him vulnerable; he had to be on his guard around Lupin. So he forced himself to scan the articles in the Prophet and presently came across the headline: Another Sighting of Azkaban Escapee! Worried Witch on Diagon Alley reports Sirius Black a regular at Knockturn!

"Snacks!" came a shrill call from the corridor, then the rumbling wheels of the trolley. "Sweets! Pies! Pumpkin Juice; warm if you want it. Snacks!"

Doors all along the carriage were flung open and Snape heard the cheery chatter and good-natured squabbling of the seniors as they denuded the trolley of its supplies. The trolley lady kept a steady hand, this scenario unchanged up to eight times a year, year in, year out.

The door drew open and Lupin looked in. "Have you eaten?" he enquired. "Had lunch?"

"Yes," Snape lied.

"Can't get you anything? The trolley's about gone."

"Thank you. No."

Lupin disappeared again, only to return moments later with a delicious-smelling pie that, having made himself comfortable on his seat once more, he devoured with gusto. Snape pretended to flick through the paper and cleared his throat to disguise his rumbling stomach.

"Why are you taking the train?" Lupin asked at length, dusting crumbs off his hands. "I'd have thought you were more inclined to Floo or Apparate."

"Why are you taking the train?"

"Well after the Dementor incident at the beginning of term, Dumbledore thought it might be an idea for me to act as the staff supervision on board. Since I was returning from London anyway. Don't tell me he asked you to do the same?"

Snape shook his head... No Apparating or Floo-ing! the Senior Healer had said to him sternly, as he'd sat on the edge of the bed, dressed once more and waiting to be released. No flying, personal transfiguring or taking of any shape-shifting potions or physically mutating spells or similar draughts of any kind. Your heart isn't up to it.

Never?

For a month, Professor. Can you abstain for a month?

Lupin paused, waiting for an answer, but Snape was staring out the window, black eyes tracking the fleeting landscape. He didn't owe Lupin an explanation. He was waiting to feel his heart, feel it beating; he'd been shocked by the unexpected damage. He'd always considered his heart the strongest part of him…it had always kept going when he hadn't needed it to.

"Are you alright?" Lupin asked bluntly. "I mean, are you well? You look -," Lupin waved a vague hand at his own face. "Peaky, I suppose."

"As opposed to? When do you transform again? The moon is waxing."

"Twelve days and nights."

"So then it is just as well I went to the Apothecary."

"Yes. Thank you."

"I'll be sure to add plenty of bitterroot."

"I'm quite convinced of that."

"And you've arranged for a substitute?"

Lupin looked confused. "For bitterroot…?"

"No – teacher. A substitute teacher. For DADA. For the three days."

"Ah. Yes. The Headmaster has offered…if urgent."

"I see. I could likely accommodate the senior years."

Lupin gave a closed smile. "Probably no need, thanks, Severus."

"I won't teach that third year group again. I don't teach hinkypunks," said Snape, folding his paper with straight, precise edges.

Lupin nodded exaggeratedly. "I know. We've discussed this. I won't call on you again for that."

"The Gryffindors never completed the homework assignment. You're too liberal with them, Lupin. If they get away with that kind of lax attitude in one class, it contaminates their attitude across them all. You'll find Minerva is of a mind with me on that."

"I, uh, did discuss that particular class with Minerva. She and I are agreed that it was an aberration. We've handled the, um, complaints."

"Complaints?" echoed Snape sharply, eyes narrowed. "What are we, are department store? And where do I go with my complaints? For instance – a good, recent example – discovering that being ridiculed to an entire class is acceptable if presented in the guise of education. Oh Professor Lupin told us it was beneficial to reduce faculty members to objects of scorn and derision, so that makes him in league with us. A cheap and lazy way to gain popularity -,"

"It's not my fault you were his boggart!"

"- and what kind of teacher appeals to the students as friends? One who can't earn their respect –,"

"Severus, you're more likely to be scornful and ridicule your students-,"

"Dark Arts is a serious subject! You – you've turned it into some kind of pantomime; you're not much more than a glorified tour-guide on the lesser forms of nasties and beasties!"

"Tour guide!? What - ?"

"Why don't you team up with Hagrid? Throw Lockhart in with his Cornish pixies and we'll have a school full of students better prepared for a circus than a war."

Lupin regarded him shrewdly, and a beat later said: "Albus warned me you might get like this."

Snape tutted loudly and folded his arms. "Referring to the Dark Arts post I suppose?"

"He said you would likely hold opinions, or, more accurately, share your opinions."

"Oh yes, the last desperate recourse of a man unable to front up with reasons to explain his own illogic. Blame the person who points out the faults. Make it so that I'm the unreasonable one."

There was a sudden, shrill whistle and then soon after the carriage was plunged into darkness as the Express entered a tunnel. While the gaslamps remained on, it was a dim light and the abrupt change acted like a suppressant on the conversation. They both glanced at the window, but found their own faces starkly reflected, the view outside now a wall of black.

Snape quickly glanced away again and stared hard at his hands. Anger had brought heat to the surface, he could feel his neck and scalp burning. Equally, Lupin stared moodily straight ahead. The chunting of the Express now seemed emphasized within the confines of the tunnel, and Snape felt the first prickles of a panicky oppressiveness and a surge of regret at having lost control. He'd unwittingly proved Dumbledore right, and the idea that he was viewed as childishly predictable infuriated him. When the gaslamps suddenly blinked out, he was almost relieved.

In the inky darkness, the train slowed and then came to a wheezing, hissing standstill and in the ensuing silence everything in the carriage was momentarily suspended while all in it waited to see what would happen, but on the third second, there was uproar among the passengers.

Snape reached swiftly for his wand, and as he muttered "Lumos," he heard Lupin do the same. Their eyes met across the deeply shadowed interior of the compartment; antipathy, but now laced with recognition that as the teachers on board, there was work to do. They stood, and being nearest the door, Snape drew it open. Together they stepped into the vestibule – now being disco-strobed by student wandlight through the windows in the compartment doors - and headed in opposite directions, each with raised voices above the ruckus of enthralled teenagers. "Settle down, settle down! Try and turn the lamps on…" "Turn that away, you're blinding me!" "Sit back down! You're supposed to be Prefects!"

"Sir! Why's the train stopped sir?" Beatrice Hayward asked Snape breathlessly in the last compartment. "Has is broken down?"

"I don't know. I expect there's something on the track and they're just clearing it away."

"The lamps won't come on, sir!" exclaimed Ross Gibberd, who had been attempting just that with his wand, and clicking his tongue, Snape stepped forward and used the same spell that had always worked without fail in the past. But, in fairness to the lad, the lamp would not light.

"Oooooh!" said one of the students, causing much mirth. "It's well spooky!"

"It's Dementors!" said Beatrice in a high voice, but she wasn't amused. "They did this before, at the start of term! They were after Harry Potter!"

"Is he on the train? I haven't seen him!"

"He is not," Snape said, no-nonsense. "He is at the castle. You are misinformed. Calm down, the lot of you, this is nothing more than an engineering problem, the conductor or engineer is no doubt on his way. Sit down and…and read a book."

He exited the compartment and gladly drew the door shut behind him. There were two sets of gaslamps, one on either side of a luggage tray on the vestibule wall, and he quickly used his spell to light them, but once more they were unresponsive. He heard hasty footsteps approaching him.

"Severus – that you? I can't -," said Lupin.

"Gaslamps won't work."

"No! You can't either?"

"Any sign of the conductor?" Snape asked.

"No…no. Do you suppose there's a blockage? Something on the tracks?"

Lupin now came before him and Snape, only half-consciously, stepped a little away. "Most likely. We should stay in the carriage, the train could start again at any moment."

"A Patronus to Dumbledore, do you think?"

Snape flashed him an irritated glance. "I'm sure we can manage a few minutes without the Headmaster. And keep your voice down. There's already talk of Dementors."

Lupin nodded. "Something similar -,"

"- happened on the last trip, I know, I know. The whole school knows, Lupin. I talked to the conductor earlier."

Snape began an advance up the vestibule, using his wand to shine a light through each compartment door and inspect the students within. Relative calm prevailed.

Lupin had remained standing on the spot. "What did he have to say? Did he say this might happen?"

"If it was planned, he certainly didn't warn me. But yes, the Dementors are frequenting the wider Hogsmeade area."

Snape paused at the door to the gangway, briefly pondering on whether to continue his examination along the other carriages. The train was full of Hogwarts students. But he turned back to Lupin. "The Dementors would have good reason for stopping this train."

Lupin frowned. "Meaning?"

"They'd have excellent cause for believing Sirius Black was on it."

And before the stunned Lupin could reply, Snape shone his wand at a nearby window and the light sparkled on the creeping fan of frost against the pane. "It's getting cold in here."

"We're in a tunnel -," said Lupin, staring at the frost in amazement. He shoved his wand-free hand under his opposite arm for warmth. "Dementors…" He turned his confused stare to Snape. "Why would Sirius be on the train?"

"You tell me, Lupin."

"Don't ask me as if I know something -,"

"He was seen in London!" Snape quickly closed the distance between them. "Seen at Diagon. The best place to buy a Nimbus, if I'm reliably informed."

Lupin shook his head. "Read that in the papers? You do realise there's been over two hundred sightings of Sirius since he escaped. Including the Tower of London and twice at Earl's Court. You shouldn't trust the Prophet so much, Severus. Unlike you."

A bright light suddenly scalded Snape's face and he turned to find several student faces pressed up against the window of the adjacent compartment door, shining their wands through and watching the teachers closely. He swirled on the spot and without speaking, stalked to the compartment belonging to he and Lupin, waiting impatiently as Lupin sauntered after.

"Ears everywhere, Severus," he commented amiably as Snape slammed the door shut.

"Where is Black? Answer me! Where is he? Where have you hidden him?" Snape shone his wand fully into Lupin's face, who shied away and raised a palm. He closed his eyes wearily.

"I haven't seen him -,"

"Of course you have!" Snape hissed. "You were with him in London. You assisted him buy the broom for Potter. You posted it from Diagon in time for Christmas, and now you've secreted him somewhere on this train. It's why you're on the train instead of Apparating; hosting an old friend back to Hogwarts, helping him as you've done all along since you got here!"

Lupin sighed. "That's simply not true."

"Hand him over to the Dementors, Lupin, before they come on the train!"

"I wish I could. Now stop this hysterical conspiratorial nonsense -,"

It was getting colder; Snape felt the probing chill seek inwards, to his bones, as if it were sentient. His breath now fogged and his teeth began to chatter. He swung his wandlight towards the window, searching for the telltale signs – a waft of tatty black cloak, a skeletal hand – but all he saw was a needlework of frost.

Energy seemed to drain out through his boots. He sank down on the benchseat and with limp arms, dragged over his winter cloak and drew it around him. Lupin watched curiously.

"You alright?" he enquired, also feeling a shiver.

"They're here. The Dementors. They're outside, looking for a way in."

"Evidently. Perhaps a routine inspection?"

"Routine? They're not organized, Lupin, they aren't following a schedule. No, they sense something. Someone."

There was a pause, unspoken words and Snape glanced up. It was hard to do, his neck felt as though it lifted lead, and when he raised his gaze he found Lupin regarding him speculatively.

"Is it you, Severus? Is it you they sense?"

"No." A weak shake of his head. "No. It's Black."

"Then what's wrong with you? You're drained, freezing – look at you, the blood's gone from your face. Why? Why are they after you?"

And, in retort, Snape scowled his hardest; but his heart…his heart…

Lupin cocked his head slightly, the faintest of smiles on his lips. "They…they view you as an escapee.."

Snape drew a ragged breath. So cold, it was so cold.

Lupin sat down suddenly and leaned towards Snape. "Is it that you were…were…one of…a Death Eater? Is it that, d'you think? Can they…? Somehow they know?"

Snape slumped in the seat so that he rested against the wall and tightened the cloak around him. It did nothing at all. Ice seemed to have thickened his blood, turning it sluggish, and his heart started to pound. He gazed into the middle distance and lowered his lids, letting his eyes unfocus. He heard Lupin but could not be bothered answering him.

Somehow they know…they know I was a Death Eater, slipped through the fingers of Azkaban like mercury, disappeared to a different prison, serving a different sentence. But I have the smell. The smell of the hunted.

Lupin had risen and was hoisting down his battered case from the luggage rack and onto the seat. Hastily he snapped open the locks and lifted the lid, then rummaged around inside. Snape was vaguely aware of it but drifted out of wakefulness. He wanted to sleep, a sleep like never before.

"Here," said Lupin briskly, and Snape felt a sensation of weight as a heavy coat was laid over him. "You need to keep warm. And here."

Thrust under his nose was a bar of chocolate. Snape jerked back a little. "What?"

"Eat it. Now."

Snape tiredly shook his head. There came a rustling sound as Lupin opened the bar and snapped off a piece. "Just eat this, a tiny bit."

Almost as much as to be left in peace, Snape accepted the morsel and put it into his mouth. It stayed on his tongue like a cold, hard brick; he hadn't the warmth to melt it. But Lupin seemed satisfied anyway. He was frowning grimly and cast one last shine of his wand at the window before saying: "I'm going out. You stay here, I'm going to see if there are Dementors on the train, perhaps find the conductor or someone in charge. I'll check on the students. Alright?"

Snape nodded, although somewhere in him, almost too weak to care, was a feeling that he didn't want Lupin to go. If a Dementor found him now, would he be strong enough to fight it? Yet Lupin accepted his nod and without further ado, opened the compartment door, being careful to close it properly behind him.

As if that would stop a creature that inhabited the crease between living and dead.

Alone, Snape shivered and positioned his wand more comfortably and in a way that afforded meek visibility in the dense, dark cabin. He could see motes drifting in the shaft of light, like frozen dust in the air, and it felt as if they scoured his throat when he breathed them in. Was it so elsewhere, or was this somehow reserved for him? Lupin seemed to have disappeared – evidently no Dementor was lurking right outside the door…then how? Why?

Shuddering all over, fingers stinging and heart dragging through each beat, Snape closed his eyes and allowed his mind to sink; whatever happened now, less resistance was less pain.

Materialising in his mind's eye, like a clearing memory in a Pensieve, he saw himself standing in a grand, dimly lit Baroque-paneled hall, the floors ornately tiled, with grim, severe portraits hung from picture rails at perfectly spaced intervals along either wall. The portraits were talking loudly, some were shouting and gesturing. Malfoy Manor. He now recognized the view of serene, pristine lawns and topiary through the row of arched windows. A frost made the buxus leaves glisten.

He was apprehensive; something had happened, something bad and he had halted in his tracks at the sound of running feet at the far end of the hall. Within moments, two men entered from a side corridor and were headed straight towards him.

"Snape! Get away. Get going!" It was Rabastan Lestrange, much younger, barely in his twenties. He was cloaked, mask in hand. His companion was already wearing his.

"What's happened?"

"Dementors -,"

The second man slowed to a fast walk and pulled up his mask as he passed, revealing a wide, manic grin. "Aurors on their way," said Crouch Junior, and waved his wand. "Lucius wants us out. He called us plague rats; infested he said. Personally I find that offensive," and then he pealed laughter.

"Barty! Come on!" urged Lestrange, pacing backwards. Their heels rang out on the floor and Snape watched them pick up speed again, headed towards the front porch which was the closest Malfoy would allow anyone to Apparate on the grounds.

The pair ran off, both masked now and as Snape watched their departing backs he noticed his breath was fogging. He glanced out the nearest window, nerves mounting and then his eyes widened fractionally as he beheld his first Dementor. It glided into view across the lawn, ragged cloak so black no aspect of folds or draping could be seen – it simply absorbed light. The long, skeletal, scabby fingers were clawed slightly before it and Snape could see the hood turning slowly left to right as it scanned. How does it search? Snape wondered, mesmerized. Can it see? Does it smell, or sense? How? How does it find its victims?

"Severus?" he heard and dragged his eyes to the end of the hall. There came Lucius, almost at a march, his expression cool and controlled. "I'd keep clear if I were you -,"

Snape quickly returned his gaze to the Dementor and Malfoy followed, pausing and then staying still and quiet a few feet away.

The Dementor drifted up close to the mullioned windows, and as it neared, each little pane inscribed its own lacework of fine ice, like a patchwork of snowflakes. Snape could see the glint of something within the recesses of its hood…not eyes, however, there were no eyes. And yet he could tell that the Dementor knew he was there. Its attention was fixed on him. It extended a nailed finger and scraped away the frost, scratching at the glass, seeming to seek a clearer view. How do you know I'm here? Snape thought, one foot stepping back. What do you know about me? Will I suffice as quarry, have I become fit for Azkaban, do you sense where I have been, what I know, what I rationalise away?

There was a soft groan from Malfoy, and Snape knew that it contained dread and misgiving. But who had he directed it to? Him, or the Dementor? Malfoy had bowed his head and wrapped his arms around himself, and now he lifted his right hand and pressed his fingers hard against his shut eyes, emitting a faint moan of endurance.

"It wants its prisoners," Snape said, the cold making his words jagged. A dreadful despair was seeping its way in, replacing the fear, and his gaze upon the Dementor became more meditative.

"It wants to feed," Malfoy replied. "Who knows who it wants. Any joy we have left, any happiness we can still claim. It wants it, but I'll make poor pickings."

The Dementor's open sore of a mouth began to gape and both skeleton hands were placed against the window, as if to brace it, the ragged ends of its cloak seaweed-like in the air behind it. Snape found it hard to look away; he was feeling drawn to it, compelled.

"No," said Malfoy gruffly, and he stepped suddenly to Snape's side and seized his upper arm. "Move. Move, just move."

"What for, Lucius? Why fight it? What's to live for?"

"Are you serious? Have you not been listening to the meetings? A new age, Severus, it's coming, you'll be in the thick of it, you'll be rewarded. I've told you, stick with me."

Malfoy dragged Snape away from the window and the foiled, frustrated Dementor ran its claws down the glass and its mouth widened to show the spiraling sickening drain of its throat, the colour of rotting flesh.

Snape's eyes opened, the taste of chocolate sweet and strong on his tongue. The half dream, half memory lingered, and he had to concentrate to bring himself back to the present, here on the stalled Express. Perhaps out there was the same creature, the very same, come to claim its lost soul.

He roused, feeling warmer and stronger, and in coming to an upright position on the bench, Lupin's heavy coat slid to the floor. He shone his wand at it, scarcely remembering how it had been laid over him. Lupin. How long had he been gone? Where was he?

Without further thought, he jumped to his feet and flung open the compartment door, shining a Lumos Duo before him. But all the beam illuminated was the interior of the carriage, the glass in the other doors now opaque, the wand-lights of the sheltering students behind blurred and blinking. "Lupin!" he shouted, and he saw movement within the compartments as the students stood and gathered behind the doors trying to see.

"Stay inside," he ordered them. "Stay where you are. Don't open the doors unless it's me or Professor Lupin."

There were no Dementors, he was glad to observe. At least not here. The chill seemed to have receded and he assumed all the action had moved further up the train. He shrugged his winter cloak on properly and drew the ties, then immediately headed off in search.

He was heading up the train, through the cars, towards the engine. All along, the student passengers had retreated deep within their darkened compartments and fastened their doors. He saw their flickering wands or small spheres of blue flame glowing through the frosted glass, indistinct figures moving about, oddly quiet and restrained.

Outside, the tunnel was pitch black but as he neared the engine, Snape noticed the darkness beginning to bleed pale, and as he went through the gangway to the first carriage, where the junior years were, there was definite daylight visible. Sure enough, the engine had been emerging from the tunnel when the train had been stopped, and as he stepped across the line Snape almost had to shield his eyes having become so accustomed to the dark. He nox-ed his wand.

There wasn't an open daylight, however, as the tracks for the Express cut through the outer edges of the Forbidden Forest on its Hogsmeade destination. Dense woodland lay beyond, heavy trunked trees, their mossy bark tinged green, became an impenetrable wall only meters from the track. In there, Snape knew, lurked fearsome things, and things more bad than good.

There had been no sign of Lupin, but the behavior of the students told him they'd been spoken to and given instruction. He reached the end of the first car, where the conductor had his seat, but it was empty and he could go no farther without disembarking. He could only assume Lupin and the train crew had gathered in the engine cab, and so he opened the carriage door and dismounted the few steps, then jumped to the ground, feet crunching on the ballast.

Within moments, he realized what was happening. There were three Dementors, and they had convened outside the cab. Lupin was standing on the ground but beginning to sink to his knees in efforts to sustain a wide but wobbling shield Patronus. He had his wand pointed at all three Dementors and was currently on the losing end of an attack with one, while the other two glided nearby, looking for a way in, desperate and undeterred by Lupin's efforts.

The engineer, fireman and conductor all watched fearfully from within the cab and as Snape ran towards Lupin he yelled at them: "Start the train! Get it moving!" At the sight of him, Lupin gave a frantic look and his shield stuttered, almost losing power entirely. "Severus, there're others, there's half a dozen or more. I can't keep this up." Without a word, Snape immediately pointed his wand and summoned a Patronus of his own, edging his forward to take over from Lupin. The combined energy drove the Dementor back; it made uncharacteristically sharp movements, like flinches, and retreated from the door of the cab.

Lupin's Patronus dropped away, giving room to Snape to advance. He could hear sounds of the train's scarlet boiler clanking into life, puffs of steam, and Lupin's huzzz as a new Patronus sprang into the air. This was enough for the Dementor to shy away, as if burnt, and the remaining two hovered indecisively.

"We leave in one minute – just got to build enough steam," the engineer yelled.

Half a dozen or more? Snape glanced around, seeing the remaining two Dementors coming towards him, apparently unconcerned about the defeat of their number seconds earlier. One approached him directly, but the other lifted into the air, sailed around and behind towards Lupin, who hastily backed up against the warm steel of the engine. Snape cast a second Patronus and directed it at the nearest Dementor, while behind him, Lupin edged towards the handrail of the steps to the cab and began to mount them.

The first Dementor came in strong and hard. Snape could see its dark shadow through the pulsing rays of his shield, and though it wouldn't be able to penetrate, it might outlast him. Behind, the second one seemed to hesitate, distracting him, and he began to inch back along the side of engine towards the steps before it encroached.

"Come on Severus!" he heard Lupin shout from the door. "We're going! Get up here!"

There was a great hiss as the engineer released the brake and the enormous wheels behind Snape groaned as they started their slow revolution. He began to jog backwards, holding off the Dementors, glancing over his shoulder to find the handrail for the steps. If he missed this moment, the train could not stop, he would be left behind.

"Severus! NOW!"

Snape stumbled over the edge of a sleeper and his Patronus wobbled. The nearest Dementor closed in towards him and its hood fell aside, revealing the grotesque head, scabbed eyes and yawning mouth in its frenetic urge to feed. Snape's heart lurched and a spasm of pain sheared up his chest and left shoulder, making him gasp. Was this his? Was this his Dementor from all those years ago, come at last to claim him? Perhaps his heart would give up his ghost before his soul could be sucked out; something had to give. Wincing, he swung his Patronus around and struck the Dementor directly, and the creature was flung forcibly away.

A quick glance showed the handrails coming towards him now, the click, huff of the wheels as the Express gathered speed and Snape turned towards it, only taking a second to put his wand between his teeth as he thrust forward his stronger hand. It connected with the cold iron of the railing and he grasped it, feeling himself jerked forward roughly as the train lifted him free of the ground. Within moments, hands grabbed at the back of his cloak and hoisted him bodily through the door of the cab.

It was a cramped space with all five of them in there, and he and Lupin were crowded uncomfortably close in the corner of the cab, but Snape still felt overwhelming relief to be moving away with speed. He looked out the door space, to see if any Dementors had decided to follow, but his eyes landed on another black object instead – the unmistakable shape of a large, shaggy dog standing on the edge of the tracks.

He lurched forward to see better, shoving Lupin aside to do so, and leaning out the door managed to catch of final glimpse as the train sailed away: the dog was watching them, and then it turned and melted into the forest.

"BLACK!" he shouted. "Sirius Black! Back there!"

"What?" cried Lupin, and when Snape swung round, wide-eyed, he found all the men staring at him.

"I SAW him! The dog! A black dog – that's his animagus, isn't it Lupin? A large black dog! It was him!"

His heart again - it throbbed and the pain shot into his throat, along his left arm. He doubled over, pressing his right hand against his chest and groaning.

"Severus? Are you alright?"

"Had a nasty shock!" announced the conductor, coming to Snape's aid by grabbing his upper arm to keep him upright. "Thinks the Dementors is dogs!"

Snape heaved for oxygen through the pain. "No…no…it was a dog, a dog, it was Black…"

"I don't think he's well," Lupin said to the conductor. "He seemed susceptible to the Dementors earlier." He helped the conductor lower Snape to a sitting position on the floor, then rummaged around inside his jacket. "I have chocolate; it will help."

Snape lifted his eyes and, panting slightly, glared. "You knew -,"

Lupin looked confused. "Knew what?"

"That he was on the train. You helped him."

With a slight shake of his head and patient smile, Lupin withdrew the chocolate bar and snapped off a portion which he handed to Snape.

"That's why the Dementors stopped the train," continued Snape, ignoring the proffered confection and gradually getting to his feet once more, now that the pain in his chest was receding. "You were here the first time it happened. You knew it would probably happen again and you could help Black escape. As an animagus they don't detect him, but as a dog he has nothing – no clothes, no food or defences. You helped him get on the train, didn't you? Where's his possessions? Did you help him get a wand while you were in London?"

Lupin chuckled indulgently, but the conductor cast his glance from Snape to Lupin with a furrowed brow. "What's 'e talkin' about? Is 'e on about that escapee? The one from Azkaban?"

"I'm afraid I don't know," said Lupin, holding Snape's glare levelly. "Professor Snape seems to think he saw something and now two plus two equals five."

"Well the Rail Authority have told us to be on a lookout for 'im!" announced the conductor, squaring his shoulders. "We was warned the Demen'ors and witch-watchers were moni'oring the Express, that 'e might try to stow away. Did you definitely see somethin' Professor?"

"Yes," replied Snape quietly. "I definitely saw something."

"Something," repeated Lupin. "That's not definite."

"I saw a dog."

"A dog?" said the conductor, puzzled. "Nah, the escapee is a man -,"

"I know that!" Snape snapped. "He's an animagus – he can change into a dog! I'm going in circles! He'll be halfway across the Forest by now, headed straight for Hogwarts – and you'll be going to meet him, won't you Lupin!"

Lupin shook his head again, resignedly, as if his tolerances were wearing thin and turned his shoulder. "Believe what you want, Severus, believe whatever makes you happy. You are aware that you can sometimes see what you want to see? What might have been a deer? A stray? Suddenly starts to look an awful lot like something that would -,"

"Don't patronize me, Lupin. Don't question my judgement."

Just then the brass whistle sounded sharply into the twilight air and a glance out the cab window showed Hogsmeade Station coming into view. Snape could see small bobs of yellow light which he knew to be lanterns, probably held by the station elves. No doubt Hagrid was there, waiting, worried.

"Merlin's pink pyjamas, eh?" said the conductor with a grin. "Ain't yer glad to see that!"

Lupin moved to the other side of the cab, carefully avoiding the fireman who straightened on his shovel, his apron and hands blackened with coal. Snape's mind was churning, the image of the watching dog on constant replay, trying to recall detail but it was already dimming, already blurry.

These draughts, Professor, the Healer had said to him at St Mungos, handing over a collection of small and carefully labelled bottles that clinked gently in his hands. Some can have a stimulating effect. Keep in touch so we can be sure the dosages are right. There can be side effects at first.

Such as? I work with potions all day – I can't have anything reactive –

No; agreed. Stick to the instructions – I'm sure I hardly need tell you that! Let us know if you feel weak or dizzy, blurring of vision, hallucinations that kind of thing…

No. No, he'd seen him. He'd seen that dog. It was no hallucination.

The Express pulled up alongside the platform at Hogsmeade Station, and Hagrid was indeed waiting, and indeed look deeply concerned, and strode along to meet the cab as the engine finally came to a hissing, clanking standstill and the whistle blew once more. The conductor jumped off first, making official announcements, and then Lupin and Snape followed, greeted by Hagrid.

"Whass happened? Why's 'ee late? Troubles? Are the kiddies aw'right?"

"Everything's fine, thank you Hagrid," said Lupin, buttoning up his jacket. "More Dementors and they stopped the train."

At this, Hagrid looked directly to Snape, an unconscious gesture for verification by a higher authority, and although Hagrid might have been unaware of it, it wasn't missed by Snape.

"It's fine, Hagrid," he responded. "Lupin acquitted himself admirably as the DADA Professor. The Dementors harmed no-one. But I'll hazard the children are hungry. See to the first-years, Lupin and I will attend to the rest."

There was a general commotion as several hundred head of student disembarked and chatted animatedly about their adventures, collected their luggage, fell into random groups and largely ignored the loud instructions from the teachers. Once they were all off the train and heading generally in the right direction, Snape once more mounted the last carriage to retrieve his own bag.

The gaslamps were alight, he found the door to the compartment he'd been in and was just about to turn the handle when it was drawn open from the inside, and Lupin stood there, his own case in hand, his book under his arm. Snape immediately stepped aside to let him pass.

"Ah!" said Lupin, at first stepping back, and then edging to the side, facing him. "Severus! Come for your things. Wondered if you'd forgotten them."

"No," said Snape, frowning. Lupin seemed odd. Formal. "No, didn't forget them." Evidently the DADA Professor now intended to treat him even more circumspectly. That was fine with him, the more distance the better.

Lupin paused at the doorway and Snape waited, but Lupin said nothing and as Snape entered, Lupin watched closely.

"Can I help you?" Snape prompted, waiting for Lupin to leave. He had no desire to walk up to the castle with him.

"No, no," Lupin replied, and ran his fingers across his moustache. He sidled backwards. "See you at dinner."

"Possibly."

Snape entered the compartment and hesitated; saw his hold-all on the rack, his paper, everything the way he'd left it. Then he heard Lupin's footsteps walking away down the vestibule. On instinct, he looked back out to check on the retreating figure.

A duffel. A duffel was slung over Lupin's shoulder, a rough canvas one, stained, the odd jumble of objects it contained causing bulges, and it bounced slightly against Lupin's back as he hurried away. A sample of something dangled from the drawstring close, as though items had been shoved in so hastily it had escaped attention. It looked like a sleeve of a dirty shirt, a sleeve with black bands printed on it.

An Azkaban shirt.

The End

a/n: Tunnel is inspired by my earlier work, The Uneven Orbit. If you enjoyed this, please check out my page for more.