It began quietly, by design. A bubble of silence, a carefully placed note, and before either of those, subtle adjustments to the guard patrol routes. They did provide the promised boost to efficiency, but they also happened to leave the windows of the royal suite unobserved for just long enough.
That hole took place in the wee hours of the morning, when only the Night Guard and other nocturnal professions of varying degrees of legitimacy were up and about. Including but not limited to students at the School for Gifted Unicorns cramming for exams.
And when all the meticulously scheduled pieces came together, the owl-silent wings of a librarian carried her up and away into the first hint of dawn.
A few hours later, the situation went from quiet to very, very loud.
Homesickness was a funny thing, especially when home was both easily accessible and impossibly far away. Sunset planned on staying in the human world even after graduation—she wasn’t sure what strings the principals had pulled to get her legitimate documentation and she was happier not knowing—but there was something comforting about being near the portal even when she had no intention of using it. Especially on a beautiful Saturday for a beautiful picnic on Canterlot High’s beautiful front lawn with the beautiful—
Twilight offered a sympathetic frown. “Embarrassing memory?”
“Something like that.” Sunset cleared her throat and tried to will the blush off her face. “”So, how are things with Timber?”
The frown deepened as Twilight glowered at the cole slaw. “I’d really rather not talk about it.”
Sunset’s own gaze dropped to her paper plate. “Oh.”
And, because apparently the universe didn’t feel that was awkward enough, two armored centurions straight out of the Roaman legions chose that moment to emerge from the base of the Wondercolt statue. They marched up to the picnic blanket with hardly any stumbling and loomed over the girls, the matching pitiless neutrality on their faces as menacing as the spears they clutched.
“Twilight Sparkle of Ee-arth?” said one.
Sunset and Twilight shared a perplexed look before turning back to the soldiers. “Uh…” said Twilight.
The other soldier glanced at his compatriot and nudged him with a clenched fist. “Why are you saying it like that? You’re an earth pony.”
“I didn’t want to assume,” the first muttered without shifting his gaze.
“Well now they’re going to assume we’re idiots.”
That got a glare. “Not if you had maintained some degree of professionalism.”
“Excuse me if the species change threw me just a little off-balance.”
Sunset, her train of thought having completed the abrupt track shift, cleared her throat and stood up. This wasn’t her first time dealing with the Royal Guard. “How can we help you, gentlecolts?”
“For the record, I am Twilight Sparkle of Earth,” said Twilight Sparkle of Earth, also getting to her feet. “This Earth, anyway. The existence of Equestria has some fascinating ramifications regarding certain interpretations of—“
Sunset cut her off with an elbow to her side. “You already told them you’re a Twilight.” They traded lopsided grins.
“Equestria needs you, Miss Sparkle,” said one of the guards, thoroughly ruining the moment.
“Please come with us,” added the other.
Twilight furrowed her brow and looked to Sunset. “Can they do that?”
Sunset, for her part, was already digging through her bag for the enchanted journal. “Unless Princess Twilight made some massive legal changes she never told me about, they can’t force you through the portal for a bunch of reasons. But they wouldn’t be asking if it weren’t something important.” She opened the journal just in time to see writing scrawl itself across the next blank page. A chill went down her spine as she took in the missive. “Okay, yeah, you should go with them.”
“What?” Sunset passed Twilight the journal. Moments later, it fell from nerveless purple fingers and nearly hit the pickles. “What!?” Twilight turned to the guards, a twitch developing in one eye. “What.”
“If it’s any comfort, Miss Sparkle,” said one guard, “that’s been many creatures’ reaction.”
“Word for word in the case of Chancellor Rarity.”
Twilight sighed and turned back to Sunset. “I don’t suppose you can come with me?”
That got a shake of the head as Sunset watched more text inscribed itself. “I’m needed here to lead the search.”
“Oh.” The disappointed tone made Sunset wince, but the plan was clear.
“Starlight Glimmer has volunteered to guide you given her own experience in this world,” offered a guard.
Sunset stood back up and gave Twilight and eagerly accepted hug. “Good luck.”
“You too.” Twilight squeezed Sunset as hard as she could manage, then pulled back with a fierce look in her eyes. “And if you find her, give her a punch in the arm for dragging me into this.”
Sunset nodded, mirroring the expression. “Already part of the plan.”
Turning into a little unicorn pony was only slightly less horrifying the second time around. Seeing it coming didn’t make it any less of a fundamentally alien experience: The surreal exchange of fingers for hooves; the hundred different wrongnesses from becoming a naked, hairy quadruped (excepting glasses and hair tie, which raised their own questions); the proprioceptive struggle to keep the horn in mind whenever her head was near any obstructions…
In short, all of Twilight’s things were once again horse things, and it hadn’t gotten any easier to deal with. Still, she had enough spare attention to notice how, rather than the expected curious crystal, the room where she found herself was built from white marble. Also filled with an assortment of cardboard boxes, dusty furniture, and other ponies.
“Welcome to Castle Canterlot,” said one of the guards, who were much less intimidating as ponies.
“Oh dear,” said a familiar voice. “This will be a challenge.” The local Rarity trotted up, giving Twilight an equally familiar once-over. “Not impossible, but a challenge. Still, you’ll do better than Trixie.”
“Trixie resents that,” pony Trixie trixied. It was the only way to adequately describe the experience. Twilight even glanced back at the mirror portal to make sure none of her classmates had snuck through.
After that, she took a deep breath and asked the question burning in her mind since she read Sunset’s journal. “Okay. So. What happened to my counterpart?”
“That’s the question of the hour, darling,” said Rarity. She looked to one of the windows. Twilight followed her gaze and, gobsmacked by the fantasy cityscape before her, nearly missed the rest of the response. “The sun went up this morning, thankfully, but there’s been no trace of her since aside from a letter she left in Spike’s room. And all that said was ‘I need a break. I’m sorry.’”
Twilight managed to tear her eyes away from the marble minarets and blurted out one of the dozens of questions bouncing around her thoughts. “Spike has his own room?”
Rarity’s furrowed brow said everything she needed to about Twilight’s apparent sense of priorities. “Of course. He is a growing dragon. Though at the moment the poor thing is going through his own contacts to see if there's been any sign of our Twilight. I fear he blames himself.”
“I see.” With another deep breath, Twilight tried to focus on something relatively sane. “Any other potential leads?”
“The Royal Guard has been preparing for a Code: Wandering Star since Her Highness’s accession was first announced,” offered one of her escorts, “but she is proving… elusive. Even by our most pessimistic projections.”
Trixie didn’t so much smirk as settle into her default expression. Which was a smirk. “They’ve already checked every library and bookstore both here and in Ponyville.”
The guard nodded. “The search will be much slower as we investigate lower-probability venues.”
Twilight nodded in turn, adjusting her glasses and trying not to think about how she was doing that with a hoof. “And that’s where I come in, right? Personal insight into the mind of Twilight Sparkle.”
The others traded uneasy glances. “Did Starlight not tell you?” said Rarity.
“Tell me what? Her message just said my counterpart was missing and there were tasks only I could perform.”
“Well…” Rarity gave a hesitant nod. “Yes, that is technically true. In the sense that we’re more concerned with the body of Twilight Sparkle.”
Twilight took a moment to consider that statement from every angle she could. Her ears folded back as she arrived at the most reasonable interpretation. “You can’t be serious.”
“Glasses aside, you are the spitting image of Sparkle circa the Ursa Minor debacle,” said Trixie.
“Which is a problem, but one some platform hipposandals and illusory wings can address.” Rarity began to circle Twilight, bringing sharks to mind.
“I’m a high school student. You expect me to fill in for your god-empress.”
Trixie rolled her eyes. “You’re overdramatizing this. And that’s Trixie saying that.”
“The princesses emeriti haven’t written back yet, but we have Discord covering the sun and moon, and he’s Pinkie Promised to keep them going at the usual rate for at least the next few days,” said Rarity, which somehow wasn’t the craziest thing that had come out of her mouth today.
“I still know nothing about your world!” Twilight cried. “Certainly nothing about its political landscape!”
Starlight trotted into the room with a smile on her muzzle that, despite knowing her for less than a week, Twilight still recognized as a sign that she was very proud of a terrible idea. “That’s where we come in! We’ve already gotten the weekend put away as a royal recess. Plenty of time to give you a crash course on who’s who and what’s what.”
Trixie moved to Starlight’s side, matching the bad-idea grin. “And even when we’re through, you’ll mostly just need to sit on the throne and look princessy.”
At this point, Cadence’s old breathing exercises were the only things keeping Twilight on her hooves. She looked longingly at the mirror portal. “What exactly do I get out of this again?”
“Besides saving a nation from abject chaos, the admiration of millions, and all the privileges of royalty?” said Starlight.
Twilight fixed her with a half-lidded glare and waved a hoof. “Hi. I’m Twilight Sparkle. Only the first entry on that list sounds even remotely appealing.”
“Ah.” Starlight nodded. “Fair.”
“You can also start establishing diplomatic ties with your world,” noted Rarity. “Our Twilight has been dragging her hooves there. She says it’s because neither world is ready to deal with all of the implications and consequences, but I think she’s just avoiding that Flash Sentry colt she refuses to discuss.”
That got Twilight thinking. “Leaving a mess for her to clean up is more tempting than I’d like to admit.”
Trixie chuckled. “I like this Sparkle. Can we keep her?”
“Still,” said Twilight, “there is the matter of school.”
Starlight shook her head, floating the other half of the quantum entanglement journal off her back. “Already taken care of.”
“So,” Vice Principal Luna said as she passed the journal back to Sunset, “Twilight Sparkle needs to act as a body double for her magical pony counterpart for the sake of national security in your homeland, and will be indisposed for the foreseeable future. Do I understand that correctly?”
“Yes, Vice Principal.”
Luna slumped in her chair. Her apartment lacked the imposing shadows of her office, but she'd been able to maintain her usual air of authority even in a ratty concert T-shirt and jean shorts, at least until now. She heaved a sigh. “I can see why Celestia foisted this on me.” After straightened both her posture and her mask of professionalism, she continued, “I assume that this will preclude her attendance at the Math Olympiad this coming Friday?”
“If it goes that long.” Sunset offered the best smile she could given the circumstances. “At least Crystal Prep has lightened up?”
Luna grimaced. “Abacus Cinch may no longer be in charge there, but…” She narrowed her eyes. “Can I trust your discretion, Sunset?”
That got a nod. “If there’s one thing I’ve maintained since my bad old days, ma’am, it’s being able to keep a secret.”
“I suppose so.” Luna took a deep breath, letting it out slowly before she continued. “Principal Cadence and I have a wager on the event, and given my confidence in Twilight, I may have agreed to an… unwise proposal.”
“Well, I’m sure it can’t be too bad—”
“If Crystal Prep wins the Olympiad, Cadence will encourage Twilight to date one of her more repentant classmates.”
It felt like Sunset had swallowed an ice cube. “What?”
Luna shrugged. “She used to babysit Twilight and is still one of her most trusted confidantes. That said, I can tell you that Timber Spruce will make another young man very happy some day.”
“Oh.” The chill kept spreading as Sunset took in the full implications. “Oh.”
“The bet seemed like the best way I could delay her,” said Luna, as apologetic as Sunset had ever heard her. “The woman’s nigh-unstoppable once she puts her mind to matchmaking. And speaking as someone with her own history of subordinating her own desires for the sake of those she loves, you have been… less than subtle.”
“I understand, ma’am.” The words felt distant, like Sunset was watching someone else say them. “If you’ll excuse me, I have an alicorn to track down.”
Luna nodded. “Of course.”