Twilight placed a shaped crystal over the lens of a webcam. With a quick spell, she bound the two together. “Let’s see if this works.” She plugged it into a USB port of the laptop computer as three fillies watched.

She launched an app to display the video feed. Nothing but blackness came through. Spike picked up another crystal and swept it past the augmented webcam. A fractal pattern flashed across a window on the computer. As Spike set the crystal back down, she said, “Well, it’s a start.”

Sweetie Belle looked up in confusion. “Why not bypass the camera and put that cable into the sensing crystal directly?”

Twilight sighed. "I really wish I could. Magical fields do not map to optical images very well. Coming up with algorithms to extract useful data out of those images won’t be easy.”

“That camera uses that cable,”Apple Bloom observed. “Why not take it apart and see how it does it?”

Twilight frowned. Not saying a word, she levitated a thick book from a nearby shelf and dropped it on the table with a loud thump. “I don’t have to take it apart. This book documents everything you need to know in order to design devices that can send data over a ‘universal serial bus,’ which is what that cable is. Actually, it also documents the design of the cable itself.” She sighed again. “It’s nearly a thousand pages.”

It was Scootaloo’s turn to give her a confused look. “So, don’t you like reading books?”

Twilight turned away and idly walked to the shelf that book had come from. “That particular book assumes you already know the contents of numerous other books,” she said, waving a hoof at dozens of other human books. It’s… it’s like giving one of Star Swirl’s scrolls to a human engineer and asking him to put it to use. He wouldn’t even know where to begin.”

“Well of course not,” Apple Bloom said, rolling her eyes. “They don’t even have magic.”

Twilight turned around and walked back. “Don’t get too smug. We’re no better off. To terminate the cable inside a sensing crystal, the crystal would have to convert what it senses into binary data and transmit that data via electrical impulses using a very complicated protocol. I haven’t been able to figure out how to do that without using their technology. Unfortunately, interfacing their computer technology to our magical technology is really hard.” She gave the webcam a flick of her hoof. “This is the best I’ve been able to come up with, so far.”

“You don’t want to know about the last attempt,” Spike said.

Sweetie Belle trotted over to the book case from which that book had come from and scanned the titles, most comprised of unfamiliar words. “I think I see what you mean.”

“Twilight, we need to talk!”

Everypony jerked their heads towards the library entrance.

“Moondancer?!”

An angry mare trotted over to Twilight, with Sunset Shimmer not far behind.

“I’m sorry, Twilight, she insisted on coming.”

Twilight focused her attention on Moondancer. “Calm down,” she said. “You can talk to me.”

Moondancer looked at the Crusaders. “This isn’t for their ears.”

Twilight looked between the fillies and Moondancer. “Fine,” she decided. “Girls, please wait outside. I’ll come get you when it’s time to leave.”

Moondancer looked at the fillies, waiting for them to go.

“Come on, girls,” Apple Bloom said. She led the others past Sunset Shimmer and to the door.

Moondancer was now looking at Spike.

“He stays.”

“I dunno, maybe I should keep an eye on them, you know, just in case.”

“You stay.”

Moondancer thought it over for a moment. “Fine, he stays.”

“Guess I’m staying.”

They waited until the fillies exited the library. Twilight closed the door with her magic from where she stood. Her attention focused on Moondancer once more, she said, “Now talk to me.”

“I want some straight answers,” she said, glaring at Sunset Shimmer.

Sunset gave Twilight a wan smile. “I think you see the problem here.”

Unfortunately, she did. This wasn’t going to be pleasant or easy. “You must understand that Sunset Shimmer is not at liberty to answer questions of that nature.”

“That’s why I’m here to ask you, princess. Don’t forget you’re the one who asked me to join, cutting-edge magic research you promised.” She let out an exasperated sigh. “But it’s all impossible!”

“There’s nothing impossible about it, I assure you.”

“How can the absence of the background magical field be anything but impossible?” With a smirk Moondancer continued. “Didn’t Star Swirl show how that field necessarily defined the base physical laws in the absence of spells to change those laws?”

Twilight winced. “He may have relied on assumptions that might have been less than correct,” she admitted. Not that humans have a good explanation for why their physical laws are what they are and not something else, never mind why their physical laws happen to be identical to our base laws.

Moondancer’s eyes had caught the laptop on the table and she pointed a hoof at it. “And what about those things? The magic behind them must be incredibly advanced—and the magic hiding it even more impressive. I’ve tried every trick in the book, and I can’t find even the tiniest hint of magic.” Her eyes locked on Twilight. “But if anypony can pull that off, you can.”

Twilight exchanged a commiserating glance with Sunset Shimmer. “You know that’s classified. You shouldn’t even be trying to reverse engineer the spells underlying their construction and operation, but I’ll let that pass because you’re wasting your time. You couldn’t find any because there’s simply none to be found.”

Moondancer silently worked her jaw before finding a response. “I don’t believe you.”

“I don’t know what I could say that would convince you.” Twilight closed the lid of the laptop. “And I don’t have time right now to try. We need to get going.” She opened the doors to the library with her magic. “Spike, go fetch the girls.”

With little more than a silent glance at Moondancer, the baby dragon waddled off.

“Going where?” Moondancer pointed at Sunset’s saddlebags. “Would it have anything to do with the latest batch of crystals?”

“Please don’t make me say it,” Twilight said as she put a hoof to forehead, rubbing it. “We’ll be back in an hour. Why don’t you go into town until then and we can talk later.”

Moondancer gave her a flat look. “How far back do we go?” she asked rhetorically. “You know you can trust me.”

“This isn’t about trust. You don’t have clearance.”

“Then give me clearance, princess!”

They locked eyes.

First Daring Do, now this. The sooner the veil of secrecy was lifted, the better, as far as she was concerned. At least the author/adventurer had stayed true to her word. And it was undeniable that Moondancer would be more effective if she had the full picture of what she had been working on. The same applied to all the other researchers. Moondancer hadn’t been the first to complain about the absurdity of their research, though none other had dared to go over Sunset’s head—but then, none other had been Twilight’s childhood friend.

Twilight broke the silence. “You do understand there will be consequences if you leak anything.” It was a statement, not a question. “I won’t be the one handling your case if you do.”

Moondancer gulped. “Noted.”

Twilight sighed. “Clearance granted.”

“What, just like that? No paper work?”

She lifted the laptop in her magic and levitated it over to herself. “Not this time.”

“Do I finally get an explanation?”

Twilight studied her. “No, but only because you wouldn’t believe me anyway.”

Moondancer snorted. “So what was the point?”

She ignored the question. “I’ll be back soon,” she said, after which she teleported.

Twilight arrived in her private residence within the castle. She put away the laptop, put on her saddlebags, then retrieved the pill dispenser from the safe. Magically unlocking it, she proceeded to turn the knob. Once. Twice. Three times. Four. Five.

Six?

“Why does this have to be so hard?” she complained to the empty room.

Despite what she’d implied, Celestia would not be the one to handle it if Moondancer broke confidentiality; her mentor would not let her off the hook that easily. Fortunately that was unlikely to happen. She wouldn’t have been invited to join the project in the first place if she hadn’t been trustworthy.

She shook her head as she relocked the dispenser and returned it to the safe. “If it’s proof you want, then proof you shall have.”

Holding five plaid pills in her magic, she teleported back to the library. Spike had returned with the Crusaders. Apple Bloom had put on her over-stuffed saddlebags. “Are we finally going?” she asked.

“Going where?” Moondancer asked, bewildered. “What about you-know-what?”

Moondancer watched with growing impatience as Twilight sent a pill to her number one assistant and to each of the three fillies, keeping the last for herself. “Well?”

“I’m getting to that,” Twilight said. “Come closer to me.” She took the pill into her mouth. The plaid taste barely registered anymore.

“Why do these have to taste so bad?” Sweetie Belle complained. Apple Bloom and Scootaloo also made faces.

“Eh, you get used to it,” Spike said. He popped into his mouth his own pill.

Twilight looked pensively at Moondancer. “Prepare to be teleported,” she informed her. She pictured a lobby in her mind. Before the unicorn could say anything, she and Sunset were encased in Twilight’s magic. “Swallow,” she told everypony. It went down with slimy ease.

Moondancer looked behind Twilight, eyeing an odd, grayish fabric wall that stopped well short of the ceiling.

“We gotta explore this!” Three fillies galloped and turned left just in time to avoid colliding with that wall.

“I’ll deal with them,” Sunset said with a sigh. “You deal with… her.” She walked briskly on two legs after the Crusaders.

Moondancer’s jaw was hanging open.

Twilight answered the unasked question. “That’s what the natives look like. This is the other, mysterious office, the one you can communicate with only via a computer. You won’t be meeting any of them today. It’s why we’re here on a Sunday.”

“And… and Sunset’s one of them?”

Twilight shook her head. “She’s just as much a unicorn as you are. Long story short, she takes this form only in this realm. If you wish to make frequent trips here, I can cast a spell on you so you do too. Not only would you fit in a lot better, you’d be able to deal with the lack of magic. Humans, as they’re called, are non-magical.”

Her jaw set as realization set in. “So this is that impossible place without a magical field.”

“That’s right,” she singsonged.

The unicorn experimentally cast a light spell. Upon seeing that it worked, she gave Twilight a smirk. “Really?”

“Yes, really. You can do that only because you’re standing near me, and because I brought a supply of magic with me.”

“How convenient.”

Twilight rolled her eyes. “Spike, follow me. Moondancer, don’t move.” They walked to the cubicles, as far as possible while remaining in sight. Twilight turned around, and saw Moondancer desperately trying to get her light spell working again.

“This has to be some kind of trick,” she said, her eyes squeezed shut in effort.

Twilight was at a loss for words. It wasn’t really any different, she had to admit, from the way most humans had trouble accepting their reality in the absence of overwhelming evidence. I need to take that more seriously.

As Moondancer continued trying to cast a spell, any spell, Twilight noticed something that might finally convince her. “Don’t worry about your cutie mark fading,” she said. “It’s a temporary effect of the lack of magic.”

“My cutie mark is what now?!” The unicorn looked at her flank and stared in horror at the mostly faded, and still fading, mark. “That’s… how… “ She turned to Twilight, furious. “You’d go that far? Stealing my magic like Tirek?! Just to maintain this fiction!”

“Oh, for…” How could she possibly think… “Spike, go to her.”

He waddled over. When he got within a few feet of her, her cutie mark rapidly returned. “See? You’re in my magic bubble now.”

Moondancer experimentally tried a light spell, and to her relief it worked. She thought it over. “Don’t move,” she instructed Spike. She walked away until the spell failed, then moved closer until it worked again. She repeated this a few more times.

“Satisfied?” Twilight asked.

“I… don’t know.” She walked over to Twilight. “I don’t suppose you have another of those pills? I assume that’s how you have magic.”

“Not with me, no, and yes it is.”

She got her phone out of her saddlebag and made a call. After a few rings it was answered. “Hi, Meg, it’s Twilight. Just thought you should know that Moondancer is here, right now, at the office. I’ve granted her clearance.”

Moondancer stared in puzzlement at what appeared to be a communication device.

“That’s fine. See you tomorrow.”

Twilight returned the phone to her saddlebag.

“That Meg?” Moondancer asked. “She comes here too, like Sunset Shimmer?”

Twilight began walking down a corridor. “The other way around. She’s a native of this realm, a human.” She looked back at the unicorn. “Keep that to yourself.”

“I see… That would explain her expertise with those computers, I guess.”

They walked to the end of the corridor, towards a window that extended the length of the wall.

“Have a look,” Twilight said, waving a hoof at the glass above their heads.

The unicorn considered the placement of that glass. “This really isn’t made for ponies, is it?”

“Nope.”

Hesitating for only a moment, Moondancer got up on her hind legs, resting her front hooves on the window sill. She scanned the surroundings, taking in the paved roads, the strips of grass with manicured bushes and evenly placed trees, and other multistory buildings presumably much like the one she was currently inside. “Not much activity.”

“It’s the weekend. Nopony lives here, and few are working.”

Her eyes followed an odd metal vehicle, moving along as if by magic. “No magic, right? How do those… vehicles move?”

“Internal combustion engine running on a liquid hydrocarbon fuel.”

Moondancer digested that fact. “Would these vehicles work in our realm? Their computers obvious do.”

“All of their technology works in our realm—with a few notable exceptions.”

The unicorn returned all four hooves to the floor. “Such as?”

“That,” Twilight said with an enigmatic smile, “is what this project is about. Sort of.” She started down the corridor alongside the windows. “Follow me.”

They didn’t get very far before Moondancer asked the obvious question. “Why are those fillies here? How could they possibly have clearance?”

Twilight stopped.

“You had to bring that up,” Spike said.

The alicorn slowly turned around, took a deep breath and exhaled. “We can thank Discord for that.”

Moondancer quirked an eyebrow. “Excuse me? Discord? I don’t remember seeing him when you passed out the pills.”

Twilight groaned. “First off, the pills are his creation—that’s a royal secret, by the way. Secondly, it’s partially my fault as I hadn’t properly secured the dispenser. The Cru—those fillies stumbled upon it and helped themselves. Since they didn’t know how to use them, they should’ve… they wouldn’t have survived.”

“Obviously, they did.”

“Thanks to Discord… in his self-serving fashion. He noticed what was happening, and since he has a soft spot for those fillies, he interceded.” Twilight rolled her eyes. “He could have simply stopped anything from happening, but no. He saw an opportunity to cause some chaos in this realm and he took it. So he directed them to Meg’s home.”

“This was a long time ago,” Spike added. “We only knew of this realm for, like, maybe a week or so.”

Twilight resumed walking. “Anyway, long story short, they all Pinkie Promised to keep it a secret.”

“Pinkie Promised?” Moondancer shook her head. “Never mind. That still doesn’t explain why you brought them here now.”

“They’re trying to get their cutie marks,” Spike said. “It’s what they do.”

This time, Moondancer stopped. “Are you serious?”

Twilight deeply exhaled. “Look, just… I dunno… This isn’t a productive conversation.”

“Clearly,” she droned.

The alicorn silently resumed walking, not checking if Moondancer followed. Only when the corridor ended at a secured door did she look back. Both Moondancer and Spike were there. She pulled a badge from a saddlebag and tapped it against the scanner, causing a loud thunk. The door swung open in her magic.

Inside, they found Sunset Shimmer setting up some equipment next to a safe, which had a prominent radiation hazard sticker on it, pausing only long enough to see who had arrived. “They’re in Meg’s office,” she said. “That should keep them out of trouble.”

“You don’t know them very well,” Spike said, as he walked past the mares into the room.

“Uh…”

“Don’t worry about it, Sunset.” Twilight followed Spike into the room. “I had a long talk with them about staying out of trouble.”

Moondancer entered last. Pointedly avoiding that subject, she said, “So what’s this all really about?”

Twilight trotted over to the safe. “In here,” she said, pointing at the radiation hazard symbol, “is a substance that, in the absence of a magical field, becomes unstable and breaks down into a different substance, releasing much energy in the process. Humans call it radioactive decay.” She twirled a knob back and forth several times, then opened the now unlocked door. “It’s not completely stable in a magical field, but the rate of decay is so small it might as well be.”

Moondancer looked warily at a box that comprised the sole contents of the safe. “That sounds dangerous.”

Twilight carried the box in her magic, removing it from the safe and putting it on top. “The box is shielded, making it safe for humans to handle. One reason humans are interested in magic is that it makes such shielding unnecessary.”

“But without a source of magic, that’s academic.” Sunset put a crystal on top of the box.

“Then I still don’t get the point. How is having an Equestrian around all the time more convenient that those boxes? And why so focused on shielding, when there’s so many other things magic can do?”

As Sunset turned on the equipment and interacted with the computer controlling them, Twilight explained: “The shielding is a nice side-effect, but that isn’t the point of all this.” She waved a hoof at the equipment to emphasize. “A magical field interacts with the weak nuclear force; that’s what suppresses decay. But that same interaction can be used to generate magic, by tapping into the energy released by the decay. The decay still happens—indeed, at a potentially vastly accelerated rate—but the byproducts no longer have the energy to do damage.”

“Since when is energy needed to generate magic?”

Sunset turned around to face Twilight. “It’s ready.”

Ignoring Moondancer’s question for now, Twilight cast an activation spell on the crystal, causing it to glow lavender. Once she finished doing that, she closed her eyes, assessing the magical environment. “If it’s working, it’s not producing enough magic to shutdown my bubble.”

She walked as far as she could from the crystal while remaining in the room. Spike joined her. Sunset checked the readings on the computer. “It is working, but the magical field strength is very low.” She watched the readings for a few more seconds. “Too low to be self-sustaining. The output is dropping off exponentially.”

Twilight tried to take it in stride. “At least we got something this time.”

“Too bad you can’t use magic to analyze what’s going on with that crystal,” Spike said.

“Why not?” Moondancer asked. “You have magic, after all.”

“Because the whole point is its operation in the absence of ambient magic.”

“But you used magic to get it started.”

“Right, to get it started.” Twilight once more trotted over the crystal and re-cast the activation spell. She quickly returned to Moondancer once that was done. “There’s no way around that, as in this realm magic cannot be generated without magical conversion of energy supplied by a non-magical source. Magic’s not even stable here; it spontaneously breaks down.”

Moondancer clenched her eyes shut as if warding off a migraine. “How is that even possible?”

“Same result,” Sunset called out.

“Okay,” Twilight said. “Might as well wrap things up unless you have any ideas.”

“Fresh out of them,” she replied. “Next step is to update the model with this data.”

With a sigh, Twilight returned her attention to Moondancer. “It’s possible because this isn’t our realm. It operates by different principles. The laws of physics here may be identical to the base laws of our own realm, but they’re immutable.” She grimaced at the memory. “I found that out the hard way. Anyway, the creation or destruction of matter or energy implies that the physical laws change over time. So, in a nutshell, in this realm, magic must respect the conservation of energy.”

Moondancer gaped at the alicorn in cognitive dissonance. “That’s absurd. If energy and matter cannot be created, then why isn’t this realm an empty void?”

“I don’t know.” Twilight walked back to the safe. “Not even human scientists have a solid answer to that, just…” She returned the box to the safe and closed the door, re-locking it. “Just a lot of speculative theories.”

She walked back to the unicorn. “Be aware that a lot of spells won’t work because of this, and even those that do—like unicorn telekinesis—work by different means.”

Sunset joined them. “I’ve uploaded the data. Let’s pick up the Crusaders and go home.”

After all four had departed the secured room, Twilight closed the door behind them. She had walked only a few feet when Moondancer spoke. “I still don’t see what the point of this is from the humans’ perspective.”

The alicorn paused for a moment, then turned around. “Remember when I said some of their technology doesn’t work in our realm?”

She nodded.

“Some of them produce these highly ‘radioactive’ substances as a waste product of power generation. It’s a really nasty problem for them. So, not only does magic make that stuff a lot easier to handle, the process of making magic actually neutralizes it. It’s the basis for our initial trade agreement.”

“Like those computers and other technologies of theirs.”

Twilight nodded. “You got it. And once we’ve figured this out, we’ll figure out what other useful things magic can do for them in this realm.”

They walked down a corridor, between those thin, bland, fabric covered walls that a tall human could easily see over. Periodically, openings on both sides—they couldn’t be called ‘doors,’ as there were no doors to close—revealed unoccupied offices. It was a temporary state of affairs, until the existence of ponies had been revealed and high security clearances were no longer required.

No sooner did they round a corner when they heard panicked voices.

“See? I told ya.”

“Not now, Spike.” Twilight instinctively teleported to Meg’s office—and remained exactly where she was. Right, she remembered. I can’t teleport outside my magic bubble.

She started galloping.

Seconds later, she arrived at the office, to find… She had to suppress a laugh. The fillies were splattered with some sort of greenish goop—and not just the fillies. The walls, desk, carpet, monitor, books… most exposed surfaces in Meg’s office were splattered. In the middle of a floor was a beaker, which still had a small amount of potion remaining. Laying beside it was a long collapsible arm with a grip on one end, currently holding a small, empty bottle.

Sunset Shimmer arrived next. She took in the scene with a frown. “Meg won’t be happy about this.”

Apple Bloom inched forwards. “That never happened before,” she squeaked out. “Ah don’t know what went wrong.”

With a sigh, Twilight tried a cleaning spell on some nearby splatter. The goop extracted itself from the fabric of the wall, to her relief. “I think I can clean this up.” The limited reach of her magic would slow the process down, but it looked doable.

“What were you attempting?” Sunset asked, as gently as she could manage, as Moondancer and Spike brought up the rear.

Apple Bloom bore a sheepish smile, as the other two stood beside her for moral support. “Well… Ah was mixing a plant growth potion outside of our magic bubbles… to see if it would still work back home… but it exploded… Ah’ve done this many times before and nothin’ like this ever happened, honest!”

Twilight deposited a blob of the failed potion back into the beaker. She put the cleanup on hold as she processed this explanation. “That’s… interesting, actually. It makes sense that magical potions would behave differently in the absence of magic. This opens up a whole new line of research.”

Sweetie Belle came forward. “Does that mean we’re not in trouble?”

“This isn’t an appropriate place for experiments like this,” Twilight stated. “Luckily, no real damage was done, but who knows what could have happened?”

“Isn’t that the point of doing experiments, to find out?” Scootaloo offered.

“Sure, in a controlled environment, when the proper safeguards are in place, yes.”

Before any of them could reply, Moondancer asked Twilight, “You didn’t know?”

Twilight looked at her, caught off guard by the question. “About this experiment? Not exactly. Applejack had mentioned to me—”

“Wait. She’s related to Applejack?”

Apple Bloom wasn’t sure where this was going. “Applejack’s my big sister,” she dutifully confirmed.

Twilight wasn’t sure either. She waited for Moondancer to continue.

“The same Applejack who’s one of your Ponyville friends?”

“That is correct,” she confirmed.

“And the other two?” Moondancer glared at the fillies.

“If you must know,” Twilight said, definitely not liking where this was going, “Sweetie Belle is Rarity’s younger sister, and Scootaloo is like a sister to Rainbow Dash.”

“Who also happen to be two of your Ponyville friends.”

Twilight had had enough. “I’ll be back in a few minutes,” she told the others. She grabbed Moondancer in her magic and invoked the return spell.

Once in the privacy of her castle’s library, she confronted her. “Get to the point.”

Moondancer huffed. “Fine. You obviously value some friendships more than others.”

Twilight blinked. “I-I admit I haven’t been the best friend in the past, the way I blew off your get-together all those years ago, but I’m trying to make up for it.”

“And this is how you do it? Keeping me in the dark while those fillies—”

“I already explained how Discord—”

“Give me a break.”

Twilight was stunned silent as Moondancer turned around and headed towards the exit. Finding her voice, she said, “What are you going to do?”

The unicorn kept walking. “I need to think about it. Don’t worry, I’m not stupid; I have no desire to spend the rest of my life in a dungeon.” A few steps later, she added, “Not that anypony would believe any of this anyway.”

Twilight just stood there and watched as one of her first friends walked out the door.

Some Princess of Friendship I’m turning out to be.

But what was she supposed to do? Knowledge of humans was tightly controlled. Her “Ponyville” friends knew about them, true, but they were involved from the beginning—and besides, they were Elements of Harmony. Unfair that might be to her Canterlot friends, that did matter.

Still, Moondancer might have had a point about the Crusaders. Perhaps their discovery of that realm was Discord’s fault, but would she have granted them visitation rights if they hadn’t been connected to her fellow Element Bearers?

Yet they did know and it had seemed harmless enough.

Twilight addressed the empty air. “You must be pleased with all the chaos this has spawned.”

There was no answer. Maybe he wasn’t listening, or…

Twilight sighed, shaking her head. Sunset Shimmer must be wondering why she hadn’t returned yet, and she needed to finish cleaning up Meg’s office.

She walked back to her residence to fetch another plaid pill.