The first thought he had when he woke up was that he was alone.

Alone. Why was he alone? Where were his friends, his family, his pack members? His ears swivelled, searching for the merest tell-tale squeak announcing a friend’s presence. His paws pressed against the ground, hoping to feel the heavy, thudding vibrations heralding a friend’s arrival. His nose twitched, sniffing the air in frantic gulps to find even a trace of a friend’s fur.

Finding nothing and no one, he lifted his muzzle to the sky, and howled, the desolate song dancing over the nearby trees in a bid to summon those elusive friends. When there was no response, he howled again, the mournful cry announcing his solitary state to all those who cared to listen.

Was he the last? Would there ever be another to share the moon-drenched night with?

With a heartfelt sigh, the creature dropped to the ground, and rested his head on his forepaws. He’d been expecting joy, and frolicking, and fun, the opportunity to forget about his worries, to just let go and . . . be! But he’d been expecting to have company for it, not to find himself apparently the only creature abroad in several miles. An unplanned whimper escaped him at the thought.

To his surprise, there was a whuff of air from somewhere to the left of him in response. Startled, his head shot up, ears pricked forward. His tail began a slow wag – perhaps one of his friends was out here after all and playing a trick on him!

But instead of anyone he knew appearing, there came instead a low growl from the bushes. He immediately tensed, his ears flickering nervously and his tail falling still. That had not sounded in the least bit friendly!

There was another growl, then a huff of disgust, and the bushes started to rustle, as whatever was in them moved away. Leaping to his feet, he let out a soft woof! Whatever was hidden might not be friendly, but at least he wouldn’t seem so alone if he could just see it . . .

A pause, and then another huff of disgust, heralded the appearance from the bushes of a creature every bit as black as he was, although this animal’s fur seemed to drink in the moonlight and smother it, leaving it as dense a black as the shadows it was emerging from. Its eyes glared at him, as it sat on its haunches with the kind of grace he’d be lucky to ever achieve. It tilted its head slightly, in a well, what now? manner.

With an excited yip, he darted forward to lip at the older animal’s muzzle. However, a rumble from the animal’s chest, and the baring of an incredibly sharp front fang, brought him up short, and he rolled over onto his back, front paws waving and his throat bared in submission. The black creature just stared down at him, then got up to walk away.

With a whine, he rolled over and pounced at the retreating tail. He wanted to play!

The older animal, though, clearly didn’t, because when his teeth were just about to snap closed on the other’s tail, he was surprised by a strong cuff on the side of his head, accompanied by a violent snarl.

Whimpering, he dropped to the ground again, curling himself into a ball. When the sharp teeth didn’t materialise in his neck as he’d expected, he looked up, only to discover the dark creature was yet again walking away from him. With a yelping whine, he leapt to his feet and lunged after the older animal, not wanting to be left alone again.

The creature stopped and lifted its muzzle towards the moon, growling to itself, before continuing onwards. He figured that was as much invitation as he was ever going to get, so he contentedly loped along in the other’s pawprints.

Unfortunately, he was so ecstatic to finally have a companion that he failed to notice when the other stopped, causing him to cannon into the other’s hindquarters with a yelp of surprise. This earned him another sharp cuff around the ear and a low, pointed growl. Whimpering almost inaudibly, he backed away, head down and tail tucked firmly between his legs. The other sniffed the air, then settled into a crouch, his eyes fixed intently on something ahead of them.

Shuffling to the side so that he could see, he realised the other was watching a herd of strange, black, four-legged animals, that looked skeletally thin, with large leathery wings. Thestrals, something in the back of his mind told him. He realised the other’s attention was on what looked to be a new-born foal, still wet from its birth and staggering around, trying to keep upright. Excitedly, he began to wiggle as it dawned on him that the other was hunting.

Just as he was about to spring out towards the tasty looking foal, a heavy paw slammed into the back of his neck, pinning him solidly to the ground. The other nipped sharply at his ear, and he barely suppressed a pained yelp. Obviously the other didn’t want his help. Sulkily, he settled into a crouch.

Sadly, the ruckus had disturbed the thestral herd, and they closed in around the newborn foal, hiding it from view. With a snarl of disgust, the other slunk away. Tentatively, he followed along, not sure if the other would tolerate his presence for much longer if he disrupted the other’s hunting. Luckily, he happened to flush out a brace of rabbits, and having caught three, the other graciously allowed him the smallest one for his own. He yelped with happiness and gratitude as he fell on it, tearing at it ravenously.

Once sated, the black other allowed him to curl up beside it in the shelter of a large tree. He fell asleep to the feel of the other aggressively grooming the fur on the top of his head.

Harry Potter woke up to discover himself wrapped in the ragged remains of his robe, just inside the entrance to one of the secret passages that led outside Hogwarts castle. His hair was disgustingly limp, and he had bits of twigs and leaves scattered all around him, but surprisingly, he wasn’t hungry. In fact, he felt stuffed.

Wondering if it was possible to sleep-binge, he crawled out of the secret passage and stealthily made his way to Gryffindor Tower.

Much to Harry’s surprise, when he reached the entrance, the portrait that was supposed to hold the Fat Lady was empty. Rotating on the spot, he scanned the other portraits on the walls nearby, hoping to see the large pink figure of his dormitory guardian. Of all the nights for her to go portrait-hopping, he fumed to himself. Isn’t there some kind of rule that says she can’t leave her portrait if someone’s out of the dorm?

When he could see no sign of the Fat Lady, he cast a quick tempus, and winced. 4 a.m. Resigned, Harry made his way to the seventh floor and the Room of Requirement. At least there he could get a comfy bed, with no snoring roommates to disturb the rest of his sleep.

In the morning, when he was finally able to gain entrance to the Tower again, he was almost ambushed by Hermione, Ron and Ginny.

“Where were you?” they all screeched, practically in unison. Harry winced – were they trying to deafen him? – and pushed through them, heading towards the stairs.

“Went wandering and got locked out,” he tossed over his shoulder, then bounded up the stairs to the sixth years’ dormitory. Surprisingly, he still managed to hear Hermione’s worried squeak as he went. Shaking his head, he grabbed the first clothes he saw in his trunk and ducked into the bathroom.

Ron and Hermione were still waiting for him when he came back down, freshly showered and changed, and with new robes. Ginny had apparently been sent on to breakfast. Hermione was biting her lip, anxiously.

“Harry, how did you manage to get out of the dorm last night?” she asked, her voice low and hushed.

Harry stared at her. “The usual way, I suppose,” he said, shrugging. “Just had trouble getting back in – the Fat Lady had gone visiting. Isn’t there a rule about that when she knows students are out?”

“She wasn’t visiting anybody, Harry,” Hermione informed him. “She’d been asked to vacate the portrait to—”

“Look, are we going to breakfast or not?” Ron interrupted. “Only, Harry’s here now, safe and sound, and I’m starving!”

“Ron . . .” Hermione started, her brow furrowing.

“Look, the man went wandering the castle, it’s not the first time,” Ron spoke over her. “So can we go now, please?”

Grumbling, Hermione allowed the lanky red-head to lead them to the Great Hall, but Harry could see that she was still worrying over something. However, she kept it to herself as they sat down and began to eat.

Near the end of the meal, Dumbledore got to his feet. “Just a little reminder,” he said, as soon as he had everyone’s attention. “Tonight is the second night of the wizarding blue moon, and so I must reiterate my warning that all students should stay safely tucked up in their dormitories tonight. You may go about your day as normal.”

Harry frowned. “What’s—?” he started, but Hermione interrupted him.

“Come on,” she said, a shrill note in her voice. “Potions first. We mustn’t be late!” And she dragged both Ron and Harry up by their arms, pulling them from the Hall. Once they were far enough away not to be overheard, though, she pulled them into a little-used alcove. “Harry, tell me you weren’t outside the castle last night!” she exclaimed, urgently.

“Why?” Harry asked, feeling even more confused. “And what did Dumbledore mean by a wizarding blue moon?”

Hermione bit her lip. “You know what a blue moon is, yes?”

“When you have a second full moon in one month,” Harry replied. He remembered learning about that in primary school, although the rest of the lesson had been spent trying to ignore Dudley’s taunts of ‘Freaky Potter must have been born under a full moon’.

“A wizarding blue moon is when you get two full moons at the same time,” Hermione explained. But before Harry could ask how that was even possible, she’d carried on, “Dumbledore explained that when he was warning us all yesterday at lunch time, as it’s even rarer than a muggle blue moon . . . so why don’t you know that, Harry?”

“I wasn’t at lunch yesterday,” said Harry. He could feel the beginnings of panic stirring in his chest. “What . . . what happens if you go outside during one?”

“They trigger a change into your animagus form, if you have one.” Surprisingly, it was Ron who answered. “There’s all kinds of horror stories of wizards or witches trying to use it to kick-start their ability to change, or even just find out what their form would be. If you can’t manage the change, or don’t have an animagus form, then exposure to the blue moon is fatal.”

“The only exception is werewolves,” added Hermione, who’d apparently been doing research on it. “It’s the only time a werewolf doesn’t change under the full moon. But if someone’s come into contact with a werewolf’s blood or saliva, then that person . . . well, it’s almost like they become a werewolf themselves, except they change completely into a wolf. A proper wolf, not like . . . not like Professor Lupin was that night.”

Harry felt himself go light-headed. Had he got it wrong? Had he actually been outside the castle the previous night, rather than stuffing himself in his sleep? And contact with a werewolf’s blood or saliva . . . the night of the debacle at the Department of Mysteries, when Remus had grabbed hold of him after Sirius . . . when Sirius . . . Both of them had been torn and bleeding at that point; it was entirely possible that some of their blood had mixed together.

“Oh, my God,” he breathed. “What did I do?”

“We’ll have to take you to see Madam Pomfrey,” Hermione said, then cast a quick tempus. “But we really need to get to Potions now.”

Harry could only stumble after her and Ron as they made their way to the dungeons. Was it true? Had he really become a wolf last night? And if he had . . . then who was the older wolf he’d seen?

They barely made it into the dungeon classroom before Professor Snape slammed the door shut. In fact, the edge of Harry’s robes almost got caught in it. Their professor was standing at the front of the classroom, his arms folded across his chest, and looking highly unamused.

“You are late,” he said, a hint of a growl in his voice. “Fifteen points from Gryffindor.” The three of them scurried towards the only empty tables left, at the back of the room, Ron muttering sulkily under his breath. “The instructions are on the board,” Professor Snape continued, waving a hand towards the chalkboard behind him, “your ingredients are set out on the table over there,” his hand moved to indicate the long trestle table set up on the other side of the room, “and at this point you should all know beyond a shadow of a doubt what you’re doing, so get to it!”

With several squeaks, the class hurried to obey.

Harry was almost overwhelmed by the scent of all the ingredients once he got close to the table. Obviously, they were all very fresh. A bit too fresh, perhaps, drawled a voice in the back of his mind. Or perhaps it’s just you. Harry ignored that thought. It wasn’t him!

But he found, as Snape stalked around the room with an even more predatory air than he usually had, that he was constantly tilting his head in Snape’s direction – almost as if he were trying to swivel furry ears he didn’t have to keep track of the other . . . uh, the professor.

“Longbottom, don’t you dare add that to your cauldron!” the professor snapped, sounding as though he were right in front of Harry. Looking up, Harry could see that Neville – three benches in front of him – had frozen in the act of holding an ingredient above his cauldron, his face white and his eyes dilating with fear as Snape loomed over him.

Snape’s nostrils flared, and Harry could have sworn he heard a low growl come from the professor. “Do you know what that is, Longbottom?” Snape asked the trembling Gryffindor, silkily.

Neville shot a terrified look at the herbs he was currently strangling. “Uhh . . . mugwort?” he squeaked.

“And you call yourself a Herbologist?” Snape sneered at him. “No, you foolish boy, that is not mugwort, but magglewert. If you attempt to brew with that, then you’ll be doing so from the afterlife.” Neville hastily dropped the herb back onto his table. “Since that wasn’t in the ingredients I set out, I wonder from whence you got it? Mr Malfoy!”

Draco Malfoy – at the next table over – jumped at being addressed so sharply. “Sir?”

“If you ever try and sabotage another student’s potion again, I shall give them yours, and you shall take a zero for the lesson. Clear?”

“But . . . but, sir—!” Malfoy stammered, clearly taken aback by the unexpected threat.

Snape spun around, his lip lifting in a snarl. “I said, is that CLEAR!” he growled, leaning over the table so his nose was less than an inch from Malfoy’s. Malfoy went even paler than he usually was, and he nodded frantically, his eyes wide with alarm.

The rest of the lesson passed in absolute silence. Somehow, Harry figured he didn’t have to look too much further for that other wolf, after all.

Giving little grunts of happiness, he wriggled on his back in the grass, the light from the two full moons dancing over his inky fur. Leaping to his feet, he shook himself vigorously, sending blades of grass flying, then collapsed back down to the ground, panting. What a glorious night to be outside! He had just completed several laps of the large stone building – castle, the back of his mind prompted – and was now beginning to think about finding something to eat.

But first, he wanted to find the other again.

Tilting his head back, he howled an invitation to the sky. His song dipped and swayed enticingly, imitating a cub’s play. The other hadn’t been very enthusiastic the last time, but maybe tonight would be different.

He lowered his muzzle to sniff the air. His ears twitched, but there was no sign the other was anywhere nearby. He howled again, calling, offering, begging. The night was made for company.

Finally, there was a short, reluctant howl from near the large, dark forest.

Leaping to his feet again, he uttered a joyful answering howl, then bounded towards the tree-line, his tail wagging enthusiastically. Several barks later, he spotted the glint of the other’s eyes from deeper inside the trees. He gave a yelp of greeting, and bounced towards the other, briefing lipping the other’s muzzle as befitted the elder creature, then leaping backwards to fall into a play-bow.

The other heaved a resigned sigh, and sat on his haunches.

For several minutes, he bounded at the other and away again, playfully snapping and bowing. The other just sat there, watching him disdainfully, but then there was a sudden blur of movement, and he suddenly found himself bowled over, rolling ears over tail. When he finally came to a stop, he staggered to his paws, weaving dizzily, and shook his head. The other was apparently still sitting where he had been, but his tail was now curved neatly around his front paws, and his jaw was hanging open, his tongue lolling out in a laugh.

With an excited yelp, he rushed forward, aiming to shoulder-bump the other, but somehow, the other’s shoulder wasn’t where he expected it to be, and he wound up tangled in the bushes behind the other. There were several soft whuffs as he struggled to free his fur from the branches, but when he finally managed it, he could see the other sauntering away, tail gently waving behind him.

Barking – which, when he thought about it, probably wasn’t the best idea – he rushed after the other, leaping and playfully growling. Just as he lunged at the other’s tail, though, the other suddenly dropped to the ground, and he sailed over the top of the other’s body, landing in a sprawling heap on the other side.

Turning to pounce back again, he was shocked at how tense and still the other had gone. He dropped to the ground and froze, watching as the other’s ears swivelled and his muzzle lifted to sniff the air currents. He couldn’t sense anything himself, but the other was older, had more experience. If the other was worried, he needed to not interrupt while the other figured out if it was safe or not.

There was a pressure in his head, like the close feeling of an approaching thunderstorm, but centred between his eyes. Shaking his head didn’t shift the feeling, and he pawed at his head to dislodge it, whining a little. The other gave a sharp yap, a command to stay silent. He managed to still the sounds in his throat, but it was hard when the pressure was squeezing ever tighter.

There was a slithering sound from the forest close by. His ears pricked instantly in that direction, and the other growled loudly, stalking over to stand stiff-legged above him. The other had his hackles raised. Whatever was coming through the undergrowth was not something the other liked at all.

As it came out into the moonlight, he could see why. It was a sickly, ugly-looking creature, looking almost like a large lizard – Komodo Dragon, his hind-brain hissed – except covered in fur. Its eyes glowed red, and it bared sharp fangs, saliva dripped from them to the grass, which hissed and turned brown beneath its feet. He felt a tremor go through him, and all the fur on his back stood up. This was wrong. Whatever this creature was – or should have been – it was wrong.

The other growled louder, warning the thing away. But it continued to advance on them. He backed out from underneath the other and got to his paws, preparing to flee as soon as the other gave him a signal. It wasn’t long in coming, and as the thing crept towards them, the other nudged him backwards, the growl rumbling in the other’s chest increasing to a violent snarl.

It all happened so fast that he couldn’t decide on the order of events until much later. The other snarled. The thing hissed. The other barked. The thing was suddenly flying forwards, fangs bared. The other was just as suddenly underneath the thing, his shoulder helping the thing to go flying off to the left, his own sharp fangs ripping and tearing at the thing’s underbelly.

There was a loud hiss as fluid sprayed from the thing in an arc. Grass, plants and trees that happened to be in the path of the fluid shrivelled almost immediately. A drop landed on his front paw, and he yelped loudly, dropping to the ground to rub it off. That stuff burned!

The thing had landed in a sprawled heap just on the edge of the forest. Treading carefully around the dangerous fluids, the other advanced on it, and pinned it to the ground with both forepaws. But just as the other was about to lean down and tear its throat out, something twanged, and an arrow barely missed the other’s snout to land in the centre of the thing’s misshapen head.

Startled, both he and the other looked at the forest edge. A four-legged animal with the top half of the two-leggers stood there, a drawn bow pointed at them all.

“We felt the menace this night,” it said, slowly. A tail swished agitatedly behind it. “We will deal with it so that nothing else will be harmed.”

The other curled his top lip at the interloper, obviously unwilling to give up his prey now that he had downed it.

“Trust, Dark One,” the interloper said. He moved forward, his bow still pointing at the downed creature. “We will not let him escape justice again. This form will be his last.”

Unwillingly, the other slowly withdrew from the creature, and began nudging him back up to the stone dwelling. He didn’t want to go, he wanted to see what this interloper was planning on doing with the creature. He received a sharp nip on his ear for his troubles, and he moved a lot faster after that.

Once they reached the dwelling, the other sat on his haunches outside the large doors, lifted his muzzle to the dying moon, and howled, a song of joy and freedom. Not understanding why, but pleased the other was finally happy, he joined in, and their combined song danced through the night as the moons set.

Harry awoke to the realisation that there was a warm body behind him, and an arm wrapped tightly, protectively, around him. He barely had time to notice the strange sensations, before they were disappearing with a curse.

“Potter!” the familiar voice spat. “What on earth—?”

He yawned, blinked sleepily, and slowly sat up. He and Professor Snape were outside the castle, curled together in their robes next to the front steps.

“What was that thing last night?” he asked, remembering how every step had seemed to kill the grass.

Professor Snape gaped at him. “You remember . . .?” he started, then fell silent. He suddenly sat down on the steps. “The Dark . . . it was Voldemort, Potter,” he said, hastily lifting the sleeve of his robe to check his left forearm. “And he is dead.” Snape shook his head, and began laughing. It held more than a tinge of hysteria. “He’s dead! He’s finally, bloody dead!” Throwing his head back, the professor howled with laughter and almost fell off the steps.

“Uh, Professor . . . ?” Harry eyed his professor cautiously. Maybe the strain of not getting his coveted position had finally unhinged the man. Professor Snape finally managed to stop laughing, and levered himself upright again, hiccupping a few times.

“That creature was Voldemort, Potter,” he said. “I’m sure Miss Granger informed you of what a wizarding blue moon does?” Harry nodded. “Consider how much Voldemort wanted the werewolves on his side, and how much he enjoyed torture. Do you really think he hasn’t come into contact with either their blood or their saliva over the years?”

Harry’s jaw dropped. Surely not! That thing had been Voldemort? There was a prophecy . . . Harry was the only one . . . how could the centaur . . . ?

“Wait,” he said, suddenly remembering the previous night a lot more clearly. “The centaurs killed him? But how could they?”

“In that form, remarkably easily,” Professor Snape said. He bounced to his feet and offered a hand to Harry. Warily, Harry took it and allowed himself to be pulled upright. “Come along, Potter! We have joyous news to celebrate!”

Following the exuberant professor into the castle, Harry wondered just how the other – Snape – would act that night, under the last night of the wizarding blue moon. He couldn’t wait to find out.