Octavia fumed, her right eye twitching violently. In her life, she had been through many horrors. In her time as a secret agent, she had gone through lengthy training, snuck into some of the most heavily guarded places in the world, fought countless thugs and done battle with fiendish villains. And she had suffered the injuries for it, feared for the safety of herself and her comrades and faced almost certain death.

But nothing had prepared her for this. This was a diabolical betrayal of her trust. This was a grievous error that its perpetrator would come to regret. This was the single most aggravating thing she had ever had to experience.

“VINYL!” she screamed, pounding on the bathroom door. “LET ME IN!”

“Just a moment, Octy!” the muffled voice of the DJ replied.

“YOU SAID THAT HALF AN HOUR AGO!” Octavia yelled, now trying the handle and finding that it was locked. She had been standing in the hallway wearing a purple bathrobe and clutching a hairbrush, a bar of soap and a bottle of shampoo for approximately the last forty minutes. “What are you doing in there, anyway? I don’t hear any water running now!”

“I’m busy! Just give me another moment!”

“NO!” Octavia bellowed. “This is preposterous! Vinyl, I’m coming in there! You will open this door on the count of three! One! ...Two! ...Three!” She waited for a couple of seconds, but nothing happened. Fed up, she placed her forehooves on the ground and gave the door a mighty buck, smashing it open with such force that a few splinters from the wooden frame fell to the floor. Vinyl started, looking at the furious cellist in stunned surprise.

Octavia gave the DJ a double take. Vinyl’s hair was its normal shades of blue, but half of it hung limply over her face while the other half was done up in its normal spiked form. Around her, suspended in mid-air by the unicorn’s magic, was a bottle of hair gel, a can of hairspray and a comb.

“You’re in here doing your hair?” the cellist asked incredulously, beside herself with anger.

“Hey, a sweet mane like this doesn’t happen by itself,” Vinyl said defensively.

“There’s a mirror in the living room! Now get out and let me take my shower!”

“But Octy!” the DJ whined, sticking out her lower lip to do her best pout. “It’s chilly out in the living room! And it’s so nice and steamy in here!”

“OUT!!!” Octavia bellowed, rearing up on her hind legs and snatching the bottle of hair gel out of mid-air before forcefully throwing it into the hallway. Vinyl yelped and dropped her other items, leaping out of the bathroom and barely managing to catch the gel with her magic before it could smash against the wall. She turned around just in time to narrowly dodge the hurled can of hairspray. However, she didn’t manage to dodge her own comb, which was thrown with such precision that it embedded itself in the DJ’s hair. The bathroom door slammed shut in Vinyl’s face, only to slowly creak back open as there was now nothing holding it closed. Left outside with her various hair care products, Vinyl sulked over to the living room.

Inside, Octavia removed her bathrobe and turned the faucet on. “How could a mare who is so unkempt spend so much time on her mane?” she grumbled to herself, grateful for the relieving sensation of warm water flowing over her back.

“So why are we going to the dungeons, again?” Vinyl inquired, keeping pace alongside her friend.

“Holding cells,” Octavia muttered. She had been in an irritable mood all morning, even when the two agents had been called in to headquarters for something urgent.

“Sorry?”

“Official vocabulary guidelines now state that we are to refer to the prisoner containment facility below agency headquarters as the ‘holding cells,’” the grey mare explained.

“...Why?” Vinyl asked, raising an eyebrow.

“Because the word ‘dungeons’ suggests old-fashioned law enforcement techniques and inequine means of imprisonment,” Octavia snapped.

“But...they are dungeons!” Vinyl exclaimed. “They’re old and underground and made of stone and have big metal grate doors! Are they still lit with torches?”

“No, thankfully,” Octavia answered as she nodded at a pair of stallions, who were standing guard at the entrance to the holding cells. “We finally installed a modern lighting system that enhances the holding cells considerably.” The guards unlocked and pulled open a heavy set of doors, allowing the two agents to proceed.

Vinyl’s description had been apt. They were underground beneath the streets of Canterlot, so there was not a single window. The walls were hewn from stone and indeed looked quite old, if clean. Lining the corridor were dozens of cells, each protected with a locked metal grate door. The only thing that prevented it from looking like an old-fashioned dungeon was the bright, harsh lighting that illuminated every inch of the room in stark detail.

“Oh yeah, this is a huge improvement,” Vinyl scoffed. “Now I can make out all the grime.”

Octavia ignored her and continued down the corridor, trotting towards the figure of Melody Maker, who was waiting for them at the middle of the hallway. She nodded at the two agents as they approached.

“Thank you for showing up on such short notice,” Melody said.

“What was so important that we needed to come down to the d-” Vinyl stopped herself. “Sorry, the holding cells for?” she corrected herself, glancing sideways at Octavia.

“Please Agent Scratch, feel free to call them the dungeons,” Melody muttered. “I’ve been working here too long to start calling it anything else.” She started trotting towards the end of the hallway while Vinyl shot a sly grin at her friend. Octavia merely scowled in response.

“What did you want to see us for, Ms. Maker?” Octavia asked, now walking alongside her boss.

“It’s that changeling you apprehended, the one who was impersonating Agent Scratch. She said she has answers, but she would only speak to you.”

“Me? But why me?” the grey mare responded, taken aback.

“Beats me, but she gave you the location of Agent Scratch.” Melody shrugged. “Perhaps we lucked out and captured the weak link in Con Mane’s group.” She led them to the end of the corridor, where a heavily fortified metal door stood. “See if you can get her to spill where Con Mane is,” she instructed, levitating a key out of her pocket and opening the door. She pushed it open with her magic before stepping back to let Octavia inside.

“Careful in there,” Vinyl warned.

“I believe I can take care of myself,” the cellist answered coldly as she strode into the room. Another bit of magic from Melody shut the door behind Octavia, leaving her alone in another corridor, similar to the one outside but much shorter. There was only one cell in here, separated from the hallway by metal bars. The agent looked inside to see the changeling lounging on the bed, staring up at the ceiling. As Octavia trotted closer, the changeling glanced at her.

“You wanted to see me?” the agent said curtly.

The changeling gave her a savage looking grin and was suddenly enveloped in a flash of green light. A second later, Octavia was staring at a perfect replica of herself. “Ah, Agent Octavia, I presume?” the doppelganger said in the agent’s voice. She stood up and began walking towards the metal bars in a perfect replication of the cellist’s dignified gait. “Forgive me, but pony tongue is far easier to speak when you’re playing the part.”

“I wouldn’t know,” the grey mare growled.

“Hmm, but this form seems to be making you uncomfortable,” the changeling remarked. “Like looking into a mirror, is in not? But no matter. How’s this, darling?” With a flash of light mid-sentence, she had changed into a replica of Con Mane. Octavia suppressed a shudder, but the changeling noticed her discomfort and chuckled softly. “My, that got a reaction. I do seem to have that effect on mares,” she added in the stallion’s voice, winking at the agent.

“I was told you may have some information. Was there a reason you wanted to speak to me, or did you just want to show off?” Octavia snapped.

The image of Con Mane chuckled. “Indeed, I do have information. But first, I need to know something.” Another flash of green light and Octavia was staring at Vinyl Scratch. “Be honest now, where’d I slip up?”

“Sorry?” the agent said, raising an eyebrow.

“How’d you know it was me?” the changeling asked eagerly. “Or rather, that it wasn’t me?” She gave Octavia a goofy grin that was such a perfect impersonation of the DJ that the grey mare had to take a second to remind herself that this wasn’t her friend.

“Why in Celestia’s name should I tell you that?” Octavia muttered, scowling.

“‘Cause I live for espionage! It’s my very life! You wouldn’t understand. You were just trained to be a spy. Me?” With another flash of green light, the changeling changed back into its original form and gave Octavia a wicked smile. “I was born to be one.”

The agent narrowed her eyes. “Not that it will matter to you any longer, but we sent a coded signal to each of our agents, something only they would recognize. When you didn’t respond, we knew you were an imposter.”

“Oh, I see,” the changeling hissed, grinning slyly. “Isn’t it interesting, this little battle of ours? Taking place right in the midst of a pony city, yet just out of sight. Oh, what it must be like to be a pony. Your minds are so placid, so inattentive, so barely used. You hardly consider your surroundings and are ruled by your emotions. And that’s what makes you so...delicious,” she remarked, licking her lips.

“Hmmm. And yet, for a member of such a superior race, you seem to be the one behind bars.”

“Perhaps, but you can’t consider yourself very secure when I can read you like a book.” Another flash of green light and Octavia was staring at herself again. “For instance, just by glancing at you I can tell you slept badly last night, are irritated with your friend and didn’t get a chance to eat breakfast this morning.”

Octavia failed to hide her surprise. “How could you possibly know all that?”

“The evidence is upon you,” the changeling smirked. “Your gait, so careful and dignified, is just a touch out of sync today, likely the result of a lack of sleep inhibiting your motions. I felt the briefest pang of annoyance from you when I transformed into the image of Vinyl, suggesting you and her haven’t been on the best of terms. Or perhaps you are and that’s just the normal state of your relationship?” she mused thoughtfully. “And then your stomach has receded slightly, an obvious sign that you haven’t yet eaten today.”

Octavia suddenly felt very self-conscious. The changeling sat on the floor, enjoying her reaction. “When you’re as skilled at impersonation as I am, you notice the little things.”

“What is Con Mane planning?” the agent asked, trying to steer the conversation back to where she wanted. With each passing second she became further convinced that this was just a waste of time and that this monster had no information to share. The changeling looked unconcerned as Octavia continued. “If you tell me, we can make life easy for you. In return for your cooperation, we can give you protection from your old allies, if that’s—”

“Protection?” The changeling laughed lightly. “I’m afraid you have it backwards. I am not the one in danger, you are. As we speak Con Mane is working to enact our revenge.”

“If you are still working with Con Mane, then why are you telling me this?” Octavia inquired.

The changeling smiled. “I wanted to learn a little more about you before Con Mane sets his plan into motion. When he is done, I assure you that I shall be on the other side of these bars.”

“What plan?” Octavia blurted out before catching herself. Her doppelganger grinned upon seeing the agent’s concern.

“Ambitious stallion, that Con Mane,” the changeling said admiringly, speaking five words in a tone that Octavia hoped never to hear herself say again. “I’ve never seen a pony with such drive. He kept mentioning her. A pony he swore to protect with his life.”

The memory of taking the Oath of Allegiance to the Royal Sisters flashed through the agent’s mind. “Con Mane couldn’t be foolhardy enough to attack Princess Celestia. She’s constantly protected by the Royal Guard!”

“The Guard? You mean the easiest armed force to infiltrate that ever existed?” the changeling replied, yawning mockingly.

“And what’s more, the princess herself is too powerful for the likes of Mane,” Octavia continued in a firm tone.

“She may be powerful, but she is not invincible,” the changeling reminded the agent. “Especially if she doesn’t see it coming. I believe our own queen proved that to you.”

It only took a second for Octavia to realize she was right. An attack that came without warning could spell disaster for even one as powerful as Celestia. Her guards, while presenting a powerful show of force, were not well equipped to repel spies. This revelation hit the agent like a ton of bricks.

“When?” Octavia asked urgently, trying to keep her tone level.

“How long have I been in here?” the changeling asked in a tone that suggested mere curiosity.

“About eighteen hours.”

“Uh oh,” Octavia’s doppelganger replied, cracking a smile that looked like she was barely managing to contain her excitement. The grey mare’s heart skipped a beat.

“What? Why ‘uh oh’?!” Octavia yelled, finally losing her temper and grasping onto the bars that separated the two. “Tell me!”

“Oh dear, I think you might already be too late,” the changeling said mirthfully.

Octavia gave one last fearful look at her impersonator before bolting for the door, galloping as fast as possible. Even in her panic, she could clearly hear the changeling call after her: “Until next time, Agent Octavia!”

“I’m sorry, but you want me to do what?” Shining Armor asked, sounding skeptical and completely bewildered. “There’s been a threat against Princess Celestia and you want me to call off my guards?”

“You can’t trust any of your guards!” Quite exclaimed, clearly frustrated at his lack of progress with the guard captain. “Don’t you understand that we’re dealing with changelings, dear boy? Until you’ve verified that they aren’t monsters in disguise, we can’t trust anypony. Especially those closest to the princess.” Both stallions were inside a pegasi-drawn carriage heading for the Canterlot Racetrack, where Princess Celestia was currently waiting for the start of the Wonderbolts Derby.

Before Shining Armor could respond, a device buried within the folds of Quite’s bowtie began beeping. “Excuse me,” he said curtly before pressing a hoof to his tie, speaking softly into it. “Agent Scratch, what’s the situation?”

“So far, nothing,” Vinyl replied, discreetly talking into the microphone on her watch. She took a long, sweeping look over the racetrack, looking for anything out of place. The stands were full of ponies eagerly awaiting the start of an exciting race. The DJ’s mane was a completely different color with the help of a little magic and she was wearing an outfit to disguise her cutie mark and blend in with the crowd. “But ‘nothing’ might not be a good thing.”

“Where’s Princess Celestia?” came the voice of Melody Maker, who was apparently listening in on the same channel as she coordinated her agents from headquarters.

“Still in her suite upstairs,” Vinyl answered, glancing up and seeing Octavia discreetly pace along the roof of the box suites perched above the stands. Elsewhere she could spot other ponies in the crowd who she recognized as agents, given that they weren’t engaged in conversation with the ponies sitting next to them or even looking down at the oval racetrack. Instead, they were glancing around the stadium, watching for something to happen. Melody had taken no chances with the princess’ safety, deploying most of the agency to the racetrack.

“I don’t like this,” Vinyl muttered. “Even with all our agents here, this crowd is big. Why doesn’t Princess Celestia just skip the race?”

“She said she committed to being there and didn’t want to disappoint anypony,” Melody groaned. “Just told me she’d be careful. I don’t think she fully appreciates what we’re up against. And if the guard has been infiltrated, we don’t want to tip them off that we know. Damn it Quite, what’s taking Captain Shining Armor so long?!”

“He remains unconvinced,” the voice of Quite answered. “Perhaps you would be able to persuade him.” Vinyl heard the scuffling sound of somepony removing a microphone before she heard a new voice.

“This is Captain Shining Armor speaking. Look, I’m personally traveling to the stadium to ensure the princess’ safety. Plus I sent another unit ahead of me to increase security.”

“Call them back!” Melody exclaimed. “The last thing my agents need is more guards to keep track of!”

“You’re telling me the princess is in danger and you want me to pull back her first line of defense?” Shining Armor said incredulously.

“I know you trust your guards, but there’s still a risk that some of them have been replaced. My agents can protect the princess, if you will let us.”

“How am I supposed to know if your agents haven’t been replaced?” the captain shouted back, clearly annoyed.

Melody groaned and put a hoof to her forehead. “Damn it, Captain, do you not think I would have checked for that before I sent out—”

“Hold it!” Octavia’s voice suddenly blurted out of the radio. Vinyl looked up at her just as the sound of fanfare filled the stadium. “Princess Celestia is coming out!”

“I see her,” Vinyl confirmed. She glanced around, noticing many more royal guards. “And it seems like the number of guards just tripled in the last few seconds.”

Vinyl heard a string of barely muffled curses coming from Melody. “Agent Octavia, stay with the princess!” the boss ordered. “Get next to her box and keep an eye on her closest guards! The rest of you, maintain sights on the crowd! Quite, stay with Captain Shining Armor. For all we know, the changelings could be targeting him too.”

“Quite,” the stallion replied.

“I’m on it,” Octavia replied, creeping silently along the roof and approaching the huge Royal Box that stood above the center of the stands. Princess Celestia stood within, looking regal as ever and in full sight of the crowd. On the cloud oval, an announcer was introducing each Wonderbolt to the crowd, who responded with applause at each of their names. At every corner of the stadium and within the Royal Box were the princess’ guards, all looking as stiff and dutiful as ever. Below, she could see Vinyl and a few other agents she recognized in the crowd.

“Racers, take your marks!” the voice of the announcer boomed over the stadium. Each Wonderbolt took their place at the starting line. With a blast of a whistle and the wave of a flag from the referee, the pegasi flew down the track, eliciting a roar of applause from the crowd.

There was a sudden crackle of static over the agent’s radio, barely audible over the sound of the audience. Octavia recognized the voice of Agent Clandestine, one of the oldest members of the force. “I see him! I see Con Mane!”

“What? He’s here?!” Octavia hissed. “Where?”

“In one of the boxes down the princess’ right side. Third from the center,” Clandestine answered.

“I see him,” Vinyl confirmed. She pressed a hoof to the side of her goggles to activate their binocular function. “He’s talking with...is that Fancypants?” The DJ immediately recognized the dapper stallion, with his monocle, tuxedo and finely combed blue mane.

“What’s he doing there?” Clandestine muttered through the radio. “He’s not in on this, is he?”

“I dunno. They’re just...chatting,” Vinyl said, watching the two stallions carefully. “And now Con Mane is trotting away, talking to some of the other guests. He looks like he’s just mingling.”

“Stay on him,” Octavia demanded. “I’ll cover the prin—”

Before she could finish her thought, there was a collective gasp and a few shrieks of horror from the audience. The cellist looked up to see one of the Wonderbolts spinning out of control, hurtling off the track and straight towards Princess Celestia. The guards sprang into action, unfurling their wings and leaping into the air to catch the Wonderbolt before he could crash into the Royal Box.

The audience remained enraptured by the sight of the guards wrestling the Wonderbolt to the ground, not understanding why they were taking such measures. Vinyl’s attention, however, went back to the stallion who was now racing through the boxes, unseen by any of the audience members and heading straight for the Royal Box.

“It’s a distraction!” Vinyl exclaimed. “Mane’s coming right at you, Octy!”

Octavia quickly jumped to the edge and peered down into the box below her, where she could see the stallion quickly yet calmly making his way towards the center of the stadium. With a single deft motion, the agent swung over the edge of the roof, catching the audience members in the box by surprise before she let go, launching herself at Con Mane and tackling him to the floor.

The agent rolled off of him and made to get up, only to see that it wasn’t Con Mane lying on the ground, but Fancypants. There were gasps of shock from the wealthy audience members in the box as the stallion struggled to rise to his hooves.

“Dear me,” he muttered in surprise, maintaining his dapper manner. “What just happened?”

“That mare attacked you!” one of the guests, a rather hysterical sounding mare, exclaimed as she pointed a shaking hoof at Octavia. “How dare you harm a pony of such prestige as Fancypants!”

The agent wasn’t buying the stallion’s disguise for a second. She drew her sword and pointed it threateningly at the changeling. “Stay back!” she ordered to the ponies in the box. “This isn’t who you think it is!”

Every audience member gasped in horror, backing away quickly from Octavia. “Guards! GUARDS!” the hysterical mare began screaming. Her shrieks quickly drew the attention of a pair of royal guards who were trotting past, on their way to assist their comrades with the struggling Wonderbolt. Their faces showed their shock as they entered the box and spotted Octavia holding Fancypants at swordpoint.

“Halt right there!” one of the guards bellowed as they both launched themselves at the agent. Despite their size, they proved quite fast. Octavia barely had enough time to dodge out of the way, dropping her sword and leaping up at the rafters, grasping on to a beam as the two guards sailed underneath. Out of the corner of her eye, she could see the changeling scampering away, unnoticed by anypony else.

With a grunt of exertion, the agent swung off the beam and flung herself at the changeling, catching him by the hind legs and causing him to fall to the ground. His head slammed against the wall, briefly dazing him and causing the creature to lose his disguise.

A piercing scream rent the air when the hysterical mare caught sight of the changeling. The monstrosity, now revealed, shook off his dizziness and sprang to his hooves, snarling at Octavia before leaping onto the handrail separating the box from the stands. Now he stood in full sight of the audience. With a snarl he leapt down into the stands.

Pandemonium broke out in the stadium. The nearest audience members shrieked and galloped away frantically, nearly trampling over other ponies in their mad dash to get out of the stadium. The guards holding down the Wonderbolt glanced up at the source of the chaos, which gave the Wonderbolt the opportunity to worm his way out of their grasp. With a flash of green light, the Wonderbolt transformed into the form of a changeling and leapt away into the thick of the panicking crowd.

Octavia jumped to her hooves and was quickly joined by the two guards as they looked down at the stands, trying to spot the changeling but unable to see anything except ponies running for their lives. The creature had vanished.

Meanwhile, Vinyl fought her way through wave after wave of fleeing ponies, trying desperately not to get pushed out of the stadium. She noticed a flash of green out of the corner of her eye and turned to see the changeling who had been impersonating the Wonderbolt transform into the form of another well-dressed audience member.

The DJ leapt across the aisle at him, trying desperately to capture him before he could make an escape. She almost caught up with him before something barreled into her, knocking the air out of her lungs. Vinyl looked up and glimpsed two panicking unicorns, a pale yellow-colored mare with pink earrings and a grey stallion with a black, curly mane and eyeglasses. The image lasted but a second before she was slammed to the ground, the sound of her goggles smashing against the concrete joining the thunder of galloping hooves and the distant screams of ponies.

Vinyl curled on the ground, throwing her forehooves over her head as a few more ponies ran around her. As the last thumps of hooves hitting the ground faded into the distance, the agent chanced a peek up. The entire audience had fled, leaving the stands completely empty save for a couple of ponies lying on the ground, apparently trampled as Vinyl had been. With a groan, the agent rolled over, holding a forehoof against her ribs while pulling her broken goggles off her head with the other.

Hovering over the stadium was a completely bewildered and concerned looking Princess Celestia, surrounded on all sides by the other Wonderbolts from the race and her guards, who were shielding the princess and keeping their eyes on their surroundings. But it was quite unnecessary, given that almost nopony was left in the stadium. Vinyl turned at the sound of galloping hooves and saw Octavia approaching her.

“Octy, where’s Mane?” Vinyl wheezed, finally catching her breath.

“It wasn’t Mane,” the cellist answered shortly, helping her friend to her hooves. “Just a changeling in disguise.”

“But...” The DJ glanced around uneasily. “Then where’s Mane?”