Big Mac sighed.

He stood awkwardly to the side of the drink table, going unnoticed by all. His eyes shifted across the room, watching from the sidelines with his head hung low.

It wasn’t that he didn’t enjoy parties. It was more that he didn’t enjoy this party in particular. He was only there to keep an eye on Apple Bloom and her friends in the first place, and that was only because Granny Smith had asked him to; he had never been great in social situations and he knew it.

He sighed again.

Just then, the Cutie Mark Crusaders darted around his hooves, under the drink table, and out the other side again. Big Mac chuckled. Leave it to them to organize a game of tag at a time like this. Heck, it even looked like they had gotten a bunch of other fillies and colts to join in; he could see them darting underneath the hooves of the older ponies on the dance floor too.

Applejack and her friend Rainbow trotted by, heading for the dessert table and the napkins that were on it. Their faces were both drenched, probably from an apple bobbing contest or something of the sort.

He looked around, and, noticing that he was still standing alone, called out her name. “Applejack!” he shouted. “Hey, AJ!”

She shot him a hesitant wave and kept on walking. He took a long, deep breath and exhaled. If his own sister wasn’t going to talk to him, then he was going to be standing here alone all night.

Okay, so maybe it wasn’t just this party in particular. He hated all parties equally.

He shifted his weight from side to side, nervously trying his best to stay out of sight. It definitely wasn’t an easy task for somepony of his stature, but he still tried. He certainly wasn’t going to be social, so he might as well lay low. That way, maybe nopony would even remember that he was there.

The constant thrum of the music abruptly cut out, followed by a chorus of disappointed groans from the crowd. Big Mac cocked an eyebrow. A few ponies headed outside to see what the commotion was about, and he followed a few yards behind.

“H-hello? Is… is this thing on?” He couldn’t see her over the crowd, but he would recognize that voice anywhere. It was Princess Twilight Sparkle. “Can you guys hear me?” she asked into the microphone.

“Put the music back on!” shouted a stallion a few rows in front of him.

Big Mac rolled his eyes.

“Um, I’m s-sorry to interrupt the music,” she said, “but I, uh, have something important to tell you all. It’s… it’s a matter of your safety.”

“Get on with it already!” shouted a different stallion in the front of the crowd.

“We can’t even see you!” the mare next to Big Mac called out.

“Oh, uh, sorry.” Twilight took to the air and flapped her wings a few times, coming to rest atop one of Vinyl Scratch’s enormous speakers.

Now that he could see her, Big Mac couldn’t help but feel bad. Her mane was a mess, and her eyes were bloodshot. The way her gaze drifted across the crowd was off-putting; she was definitely looking for something. For what, he wasn’t sure.

What he did know was that she looked unnerved. Worried. Scared, even.

His eyebrows furrowed. What in Equestria could have a pony like Princess Twilight Sparkle scared?

Twilight’s wings flitted at her sides, and she scanned the crowd once more. “I hate to, uh, ruin the party, but I’m worried for everypony’s safety. I… I  h-have reason to believe t-that there are chan—”

One of her and Applejack’s other friends—the yellow pegasus with the pink mane—dove straight into Twilight full-force, knocking both of them off the impromptu pedestal. The crowd quickly parted, and they rolled a few times before coming to a stop right in the middle of everypony. The pegasus pinned Twilight down. Twilight let out a shriek of surprise, and the whole town went painfully silent.

The pegasus leaned in to Twilight. Once she was a mere inch away, she bared her fangs and snarled.

Fangs? Big Mac had to do a double take to make sure he was seeing what he thought he was seeing. What in the name of Celestia’s going on?

Just as the pegasus—Fluttershy, he recalled—was about to sink her teeth into the other mare, Twilight disappeared in a flash of blinding white light.

She reappeared a moment later on top of the same speaker Fluttershy had knocked her off a few moments earlier. “Changelings!” she frantically shouted. “There are changelings among us!”

Fluttershy let out a guttural shriek and lunged at the princess. Somewhere along the line, her gentle, flowing mane and delicate coat disappeared, only to be replaced by a hard, crusty, black exoskeleton.

He lurched back a few steps. There really were changelings among them. He spun around, looking at those standing around him in a mixture of anger and fear.

He could no longer see Twilight, but he could hear her screams. Nopony did anything—they just stood there in shock, listening to the horrible fight raging in front of them.

After a moment, the local confectioner, Bon-Bon, pulled herself on top of the DJ’s speaker. She smiled a wicked grin and then, in the blink of an eye, she changed into a bug-like creature nearly identical to the one who had attacked Twilight. The creature who was once Bon-Bon reared up on its hind legs and whinnied, assuring that it had everypony’s attention. Once the changeling knew all eyes were on it, it shrieked, “Riiiot!”

Bon-Bon lunged into the crowd at another pony while making a sound that could only be described as a war cry. A few ponies in the crowd revealed themselves as changelings immediately afterward, who were then followed by a few more. At first it was only a trickle of not-quite-ponies, but that stream soon turned into a flowing river. In hardly any time at all, he was looking out over a sea of black, equine-sized bugs.

He staggered backward. Nearly every single pony, minus a few splotches of color interspersed throughout the crowd, was a changeling. The ponies—former ponies, rather—around where he stood closed in. His world began fading to darkness, and he fell to his knees.

One of them made a repulsive chittering sound, and before long all of them joined in. It took him a moment to realize it, and when he did, his head drooped even lower. “They’re… they’re laughing at me,” he muttered.

“You ready, Pony-Boy?” one of them spat.

“Just… make it quick, please,” said Big Mac.

“No,” came the response. He wasn’t even sure which one of the five or six creatures muttered the singular word, but it didn’t matter. The outcome would be the same either way.

Suddenly, his head shot up. His heart leapt into his throat. One thought and one thought only permeated his consciousness: “Apple Bloom.”

That was when Big Mac’s whole world fell apart.

He had to save her. Granny Smith had made him promise. He’d promised that he would watch after her. That he’d keep her safe. He had to save her. He just had to.

One of the changelings snapped at his ear, jerking him from his thoughts. Before it could land an actual bite, Mac spun around on his hooves, reared up, and bucked it square in the face with all force he was capable of. The changeling’s head whipped back like a bullet. There was a sickening crack as its neck twisted beyond its breaking point, and it fell to the floor, limp and lifeless.

The other changelings stopped their chittering. They stared at him, and he stared at the corpse. It’s head was twisted one hundred eighty degrees, so that it’s chin was facing skyward. Part of the spine was protruding from its neck and green blood was spurting out from the opening, pooling around them.

Big Mac had to fight back the urge to vomit.

Had… had he done that? Was he really that powerful? Changeling or no, that just wasn’t right. Nopony should have to kill another creature, especially like that.

But he didn’t have time to worry about the senselessness of death. He was on a mission. He had to find Apple Bloom. He had to bring her home. Just like he’d promised.

The changeling behind him crouched, preparing to pounce. He sensed its movement and dropped to the ground, just low enough that the creature grazed over his head. Before it crashed into the ground on the other side of him, however, its wings flapped. It flew up into the air, flying just out of Big Mac’s reach.

“Horseapples,” he muttered. “Of course the little buggers have wings.”

The changeling on his left made to take to the air. Before it could, Mac jumped back to his hooves and threw all his body weight at it. They rolled a few feet before coming to a stop, and Mac pinned it to the ground. He wrapped his forelegs around it’s neck and held it still, so that it could only writhe in his grasp.

Time slowed. He didn’t want to do it. But he had to. For Apple Bloom. He’d promised.

He clenched his eyes shut and clamped his teeth down on its plastic-like wings. Once the changeling realized what was happening, it squirmed even more, trying to escape fate. Somepony let out a weak whimper—whether it was Big Mac or the changeling, he didn’t know.

He clenched his eyes even tighter and yanked. The changeling’s wings tore like cardboard. It was over just as soon as it had begun, and Big Mac dropped the changeling onto the ground. It laid there, wallowing in its own pain and blood. He shot it a sympathetic look before spinning around, ready to take on another.

One of the other changelings was buzzing around just out of reach. Big Mac let out a primitive growl. He jumped and swatted at it with a hoof, but came up a few inches short.

He whipped his head around, looking for something, anything to knock the airborne monster from the sky. Eventually his eyes settled on the drink table nearby, and he darted over. He grabbed a few empty hardwood mugs and began throwing them.

The first one skimmed the changelings head. The second one was a foot too low. The third one hit it square on the forehead, knocking it back a few feet and leaving a nasty gash. Before it could regain its composure, one final mug clipped its wing and the changeling came spiralling down to the ground.

Before he could celebrate the minor victory, however, another changeling threw itself onto Big Mac’s back. He flipped and flailed wildly, whipping around like Pinkie Pie on a sugar high. Still, the changeling held fast, and Big Mac couldn’t shake him.

Instead, he flipped forward, landing on his back with the changeling underneath him. It let out a fleeting squeal and let go of Big Mac, who then rolled off the changeling. He climbed to his hooves and looked down at the pathetic creature, squashed underneath his impressive weight. With a sigh, he looked up, ready to take on his next challenger.

His eyes bulged. Surrounding him were ten more changelings who had taken the place of their fallen comrades, ready to take him on.

He cursed under his breath. Fighting changeling after changeling was getting him nowhere. He needed to find Apple Bloom. He needed her to be safe. He’d promised Granny. He had promised.

He tensed up, then barrelled through the wall of changelings. His head swung from side to side, searching for a little red-and-yellow filly. The place was nearly empty at this point. Bodies of changelings littered the bakery, and the place reeked of sweat and fear. The stove was on fire behind the counter, and it was rapidly spreading.

Apple Bloom was nowhere to be found.

But Princess Twilight was.

The swarm of bugs still hot on his trail, he darted across the room to where Twilight was grappling with the changeling: likely the same one who had imitated Fluttershy what felt like a lifetime ago.

The changeling once again had Twilight pinned, and was snarling and snapping at her neck. She was weakly pushing it back with her hooves. Big Mac could tell that she was fighting a losing battle—the matching bite marks on either side of her neck made that obvious. It was a miracle that she was still conscious.

He wrapped a foreleg around the changeling and tossed it in the other direction. After shooting a nervous glance backwards, he quickly lifted Twilight to her hooves by the scruff of her neck.

“Get outta here, find somewhere to hide,” he breathed. The two galloped full-speed toward the exit, bursting out into the open air of the Ponyville Plaza.

Outside was even worse than inside. The place was a battlefield. While Sugarcube Corner had been a graveyard, the streets were very much alive. Cries of both pain and victory rang out, assaulting his ears. Ponies fought with imitations of themselves. There was hardly any room to breathe, let alone think.

It was pure, unadulterated chaos.

It was a riot.

“I… I have to go,” Twilight mumbled. “I… I’ll be back.”

Suddenly, she was gone. So were the changelings, off to join the enormous fight laid out before them like a buffet of death and decay.

He scanned the crowd. That familiar bow-wearing filly was still nowhere to be found. If she wasn’t in plain sight, there was no way he was ever going to pin her down. There was a whole town she could be hiding in. Still, he had to try.

“Where would a filly hide at a time like this?” he muttered.

Suddenly, it hit him. “…Home. She’s at home!”

It took him a moment to get his bearings, but once he did, he took off down the street like a big red bullet straight from a gun. He shot past Town Hall, past Bon-Bon’s Confectionery, and past the Carousel Boutique. He charged right out of town and down the path to Sweet Apple Acres, never stopping to catch his breath. He was on a mission. He had to find her. He had promised.

Tired and out of breath, he flung open the door to the house. Peacefully sitting in her rocking chair was Granny Smith, knitting another something or other.

“Granny,” he managed between gasping breaths, “you seen AB?”

“Weren’t you watchin’ her?”

Big Mac took a deep breath then exhaled slowly, trying to calm himself down. “Y’see, Princess Twilight got up in front of everybody and told us that… there were…” he trailed off, eyeing Granny Smith suspiciously.

“She told you that there were what? Sweet Celestia, I know you’re quiet, boy, but at least finish your own dang sentence.”

He pursed his lips. There was no point in dancing around the subject. It was best to just come out and say it. “G-Granny? Are you a changeling?”

There was a long, painful silence. Big Mac's resolve stretched thinner and thinner with every second that ticked by. His heart sunk deeper and deeper into his chest.

In lieu of a response, Granny Smith hopped from her chair with the agility a mare of her age couldn't possibly have.

"Dammit," Big Mac muttered under his breath, his head dropping down.

When he looked up, a changeling stood in her stead: a comically large changeling. It was easily Big Mac's size. It's glowing, beady, red eyes bored deep into Big Mac.

"Where's Granny." It wasn't a question. It was a demand.

"I'unno," the changeling replied. "That's not my job."

"Then whose job is it?"

The enormous changeling bared it’s fangs and let out a feral hiss. Big Mac instinctively knew what was coming and took off down the hall. The changeling came barreling after him.

He darted into the kitchen and took a sharp left. The changeling came bounding through after him, but, expectedly, made the turn a little too wide. He heard it fly into the table and take a nasty spill, but he never turned around to see for himself.

Big Mac skidded around the kitchen and back into the family room. After quickly grabbing Granny’s rocking chair in his mouth, he placed himself beside the door frame.

The changeling grumbled and jumped to its hooves. After a moment of catching its breath, it charged through the doorframe in search of him.

Just as the changeling was through the doorframe, Big Mac transferred the rocking chair to his hooves, stood up on his hind legs, and brought the chair back down on the changeling’s head all in one fluid motion.

After what should have been a skull-crushing blow, the changeling didn’t even flinch. It’s head cocked to the side, and, after a moment, it let out a low growl.

Big Mac let out a whimper.

This was not a fight he was going to win.

Without a second thought, Big Mac bolted out the door. Sure, he had no chance of beating the monster changeling in a fight, but he could probably outrun it. And, if he made it to a good enough spot, he could probably hide until it left… and he knew exactly where to go.

Out the door. Down the steps. Over the hill. Around the barn. Through the propped-open cellar doors. Stop and breathe.

After slamming the cast iron doors shut behind him, he bolted them and hid in the corner of the ten-by-ten room. It was small, but it was built for weathering the most powerful of storms. The door, barring the use of powerful magic, was impossible to open. The walls were two feet thick and made of concrete; they were virtually impenetrable. Enough food to last a family a week was stored in boxes all around him. He was set, at least for the time being.

After a moment, he could sense the presence of the changeling outside the cellar. It chittered and threw itself at the door once, twice, then three times. Just it was about to launch itself a fourth time, it stopped. The door hadn’t budged in the slightest.

There was a terrifying moment of nothingness. Big Mac’s heart stopped beating and he couldn’t breathe.

The monstrous changeling threw itself at the doors one last time. This time, it made a dent.

He winced. That was definitely going to be one nasty bruise later.

Big Mac heard sigh, then the sound of wingbeats filled the air. He was alone once more. It was only then that he finally allowed himself to breathe again.

Still, he didn’t dare leave the shelter. The changeling could have flown just out of reach, or maybe it would be back later. He just couldn’t risk it.

Alone in the darkness, he found himself lost in his thoughts. How long had Granny been a changeling? How long had everypony been a changeling for that matter? Was he the only true pony in Ponyville?

What about his sisters? If Granny was a changeling, then there was a pretty good chance that Apple Bloom and Applejack were too. It was no secret that they got out a lot more than he did, so it made sense. Hell, one of those changelings he took out back at the party could have been the fake Apple Bloom. The irony of it all wasn’t lost on him.

He sighed.

What was he going to do? He could survive in the shelter for a couple weeks, sure. But after that? He would have to leave the shelter to restock. He could try to pass himself off as a disguised changeling, but then he’d only end up back in the shelter for another few weeks. It was an endless cycle.

The whole town—the whole country, even—might be in shambles. Could he survive that? Did he even want to?

No. It didn’t help anypony to think like that. Princess Celestia was probably on her way to Ponyville right this very minute. She would sort out this mess. She always did. Maybe she could find other survivors like him.

Maybe she could save his family…

His eyes fogged up, filling up with the tears of a life lost. He looked up at the ceiling trying to fight back the inevitable fall, but it was to no avail. The gravity of the day’s events finally settled deep in his gut, and the tears started flowing.

“It all happened so fast…”

He didn’t know many things, but he did know one thing for sure—his life would never be the same again.