Those Who Dwell Under The Hills

The business of the library occupied the rest of Twilight’s day. Through all of the stacking, sorting, shelving and reshelving, however, her mind was taken up only with the photographs.

Changelings. The last time anypony had seen Changelings was many years before, during the failed invasion of Canterlot. Oh, there were sightings, there were always sightings. Somepony dizzy on liquor and salt might stagger home swearing he saw a Changeling following him down the road. Another might contend that her very special somepony had been replaced by a Changeling, claiming she saw his eyes turn green right before he left her. None of the claims ever amounted to anything.

This was different. These pictures were real evidence that the Changelings had returned, and not just some stray, or a solitary sad creature hiding among ponies, but three, and they had died violently. How many more were there?

Twilight worked through the day. She wore her agitation openly and found herself making spurious excuses to the patrons and friends that came through the library. By the time nightfall and the end of the day’s business came she felt exhausted in mind and body.

Dusk glowered outside the library, the darkening red glow of twilight shimmering from the metal paneling of the adjacent buildings. A purple-wreathed broom listlessly swept stray dust toward the open front door, out into the growing darkness. Only barely conscious of her own sweeping, Twilight remained consumed with the horrible photos, so much so that she very nearly swung the broom into the legs of a green unicorn who came bouncing down the short walkway to the library, seemingly from nowhere.

Heedless of the late hour or Twilight’s obvious attempts to complete her workday, Lyra Heartstrings bounced through the door, grinning in her usual cheerful manner. She started pacing slowly around the front room of the library, tilting her head back and forth as she looked at the books. Twilight watched her in confusion, sweeping forgotten.

“So, Lyra...” Twilight began after a moment. “What’s up?”

Lyra turned and bounced quickly across the library, as if she’d been waiting for Twilight’s acknowledgement. “Up?” Lyra asked. “Well, there’s clouds, rainbows, the sun, the moon, stars. You should know this, Twilight!” She grinned at Twilight and began rocking back and forth on her hooves. “Lots more things, too! I’ll bet you even have a book on things that are up.”

An involuntary sigh escaped Twilight’s mouth. Lyra had been a Ponyville fixture as long as Twilight could remember and was friends with nearly as many ponies as Pinkie Pie. Unlike Pinkie, however, Lyra was able to use the same age-regression magic as most unicorns and so showed neither her age nor any sign of calming down.

“Um... Alright, can I help you with anything?” Twilight said slowly, as if she were speaking to a particularly slow foal. “I was just about to close up the library.”

“I just wanted to talk to you for a minute!” came the aggressively cheerful response. “Oh, could you close the door? It’s getting late, you know!”

I hadn’t noticed, Twilight thought to herself bitterly. She reached out with her telekinesis and nudged the front door shut with the sweeping end of the broom.

Instantly, Lyra stopped her rocking, her expression hardening. “Quiet,” she said, in a low and serious tone that Twilight had never before heard from the mercurial unicorn. She turned and walked away from Twilight, stepping carefully around the edges of the large front room

“What?”

Lyra didn’t turn to face Twilight as she snapped back. “Quiet! I need quiet for a second.”

Twilight simply stood, watching in confusion as Lyra - silly Lyra, cheerful Lyra, bouncy and ridiculous Lyra Heartstrings - marched crisply and deliberately around the room with the demeanor of a police officer or city guard. Her horn pulsed with quick bursts as she walked, pulling books out telekinetically and putting them back, or flipping small objects in the air before restoring them to their previous locations.

Eventually, she completed her circuit and walked up next to Twilight. Her horn flared brightly for a moment, and Twilight felt her muscles tense as a sensation of intrusive magic washed over the library.

“Twilight,” Lyra finally said, in a barely-audible murmur. “I’m picking up three passive listening devices behind that door.” She jerked her head toward the heavy wooden door that led to the basement. “Know anything about that?”

Listening devices? “What do you mean?” Twilight replied, matching Lyra’s tone. “That’s my laboratory, I have lots of equipment down there. What kind of devices?”

“Anything,” Lyra muttered sharply. “Microphones, dreamcorders, anything like that. Anything for picking up audio or magical field fluctuations.”

The tension in Twilight’s muscles eased somewhat. “Well, I have two dreamcorders and an old crystal-set field analyzer.”

Lyra looked at Twilight with a furrowed brow and the sort of confused expression Twilight often imagined she herself wore when dealing with the loopy musician. “What do you need two dreamcorders for?”

“They’re-” Twilight sputtered. “They’re my two prototypes! I’d have three except I sold the working model to FFI along with the design! Lyra, what is going on here?”

“Changelings.”

Twilight’s brain ground to a halt. The sound in the library seemed to deaden at that one word. The two unicorns looked at each other quietly. Lyra’s expression was once again blank and impassive.

After a moment of oppressive silence, Lyra spoke again. “Princess Cadance sent me.” She turned and began slowly pacing around the library again, tension plainly visible in her withers and croup. “She got your reply to her- You know,” Lyra said. “We need your help.”

“My help?” Twilight asked. “With what? Where did those photos come from? Do we need to gather the Elements of Harmony again?”

“No!” Lyra snapped. She turned to face Twilight again. “No, we want to keep this quiet. Quiet, do you understand?”

“I understand, but keep what quiet? What ‘this’?” Agitation was once again creeping into Twilight’s voice.

“I-” Lyra paused and sighed, then exhaled. “Alright, it all started three weeks ago. There was a maintenance crew down in the train tunnels near Fillydelphia. They were just going down to replace a length of damaged track...”

The train tunnel outside Fillydelphia was identical to the other tunnels that connected the nearest cities to Canterlot, a dark, tiled vault over parallel rows of steel tracks set on concrete ties. The tracks themselves hadn’t changed much from the trains of yesteryear; besides acting as guidance for the levitation trains, they still had to accommodate other types of traffic on occasion and so were recognizably train tracks. The tunnel was comparatively new, having been bored through a bare few years earlier, so the tiles, tracks and ties were only beginning to show any kind of wear or corrosion.

Narrow Gauge walked slowly in the darkened tunnel, staying close to the little motorized railcar loaded with the maintenance crew’s equipment and, more importantly, only source of light. Other than the railcar’s lamp, darkness in the tunnel was total. Silence very nearly reigned, too; the gentle crunch of hoofsteps on gravel and the faint rumble of the railcar were the only things to remind Narrow Gauge that he was not, in fact, stone deaf.

The group proceeded down the length of the track, heads held low, tails swishing nervously. The light from the lamp chewed at the darkness ahead. At the edge of the light, where it was swallowed by the tunnel, Narrow Gauge imagined that he could see things moving. When the area was fully illuminated, of course, nothing was there. The hardened old railpony couldn’t decide if that was comforting or not.

“We should be comin’ up on the damaged track soon,” he said, more to hear himself speak than anything else. The noises of agreement from the rest of the track crew were entirely too enthusiastic; they, too, were happy enough to hear anything at all.

The hazy light of the lamp illuminated the track ahead as the crew approached the designated work site, section 57 eastbound, where one of the rail conductors had reported a discontinuity in the track. The levitation trains were much more resilient to track damage than the old steam locomotives. Juddering and requiring manual guidance over the gap was much preferable to a disastrous derailment. It was still dangerous, however, and as soon as the report came in the track crew had been dispatched. What the light illuminated, however, was not a broken length of track at all.

“Boss, it’s a pony!”

Narrow Gauge and his crew quickly halted the railcar. Indeed, a pony lay across the track, just barely visible at the edge of the orange lamp light. From what Narrow Gauge could see, the poor pony was a pegasus, wings splayed out behind it, the rear half of its body gracelessly draped across one of the pristine rails. Its coat was dark, but even at this distance Narrow Gauge could tell that whatever had happened to this pony wasn’t pretty. He’d seen more than a few train accidents over the years. Another benefit of the new trains, he thought. They leave a nicer looking body.

Shaking his head sadly, Narrow Gauge re-engaged the railcar, allowing it to creep forward at a slow crawl. “Steelshank,” the large earth pony called out, louder than necessary, “get the incident log. We’re gonna have to get somepony else down here to deal with this but I want it written up proper.”

A muttered ‘right, boss’ came as the incident notebook lofted up from the railcar and floated away from Narrow Gauge to the unseen unicorn worker on the opposite side of the track. Narrow Gauge barely took notice of this, however, as the light more clearly illuminated the pony the group was approaching.

What Narrow Gauge had taken for a dark coat was not hair at all, but chitin, black with green showing through gaps in the hard plates. The rough shape was right, but where he had expected to see feathered wings were instead tattered, veined membranes. A crooked and warped horn jutted from the ‘pony’s’ forehead, above a pair of green-tinted compound eyes that glittered like gemstones in the light.

“Boys, turn around,” he said, bile rising in his throat. “We’re leaving. Shank, write it up when we get back home but we are gettin’ outta here now.”

Three pairs of questioning eyes shone in the darkness as the crew looked toward Narrow Gauge in confusion.

“What in Tartarus izzat thing, Narrow?”

“A Changeling,” Narrow Gauge said, even as he kicked roughly at the big lever that would reverse the railcar’s drive. “It’s a Changeling.”

“What was it doing down there?” Twilight asked. At some point during Lyra’s explanation, she found herself sitting on her hindquarters on the wooden floor of the library.

Lyra herself had resumed pacing about the library slowly, hooves clicking deliberately against the hardwood. “We don’t know. We managed to get the incident report suppressed and the body transferred to Canterlot, but we still haven’t even really begun investigating what actually happened.” Lyra stopped and sighed loudly, then reversed the direction of her pacing. “Not only that, but you saw the photos. We had two more incidents in the following weeks that we had to clean up.”

Twilight was silent for a moment as she watched Lyra.

“Why me?” she asked finally. “If we’re not planning to use the Elements, how am I supposed to help? I’m no policepony.”

Lyra ceased her pacing and unceremoniously draped herself over a small table in the center of the floor, looking at Twilight upside-down. “You’re a brilliant researcher, that’s why. You also have more experience dealing with these kind of threats than anypony other than the princesses themselves. You saw right through Chrysalis’s disguise the first time the Changelings tried something like this. As soon as we started planning this investigation, Princess Cadance wanted your help.”

“I’m not sure about all this. I really think I should speak with Princess Celestia-”

“No!” Lyra shouted, rolling off of the table with a loud thump and clambering quickly to her hooves. “No, Twilight, you can’t do that.”

“What? Why not?”

Lyra sighed again, dropping to her haunches. She stared forward dully, her eyes fixed at a spot on the floor between herself and Twilight. “Twilight, Princess Celestia’s been compromised. That’s the other reason we need your help.”

“What? Wait, you mean-” Twilight’s eyes grew wide, and her voice dropped to an urgent whisper. “Has Princess Celestia been replaced?”

Lyra shook her head and Twilight’s heart slowed slightly from its hammering beat. “No, but we think somepony in her staff has. We suspect either one of her guards or somepony else who works closely with her.”

“And I suppose,” Twilight quietly rejoined, “that there’s been no luck either finding or expelling the Changelings magically.”

“Just like last time.”

Twilight nodded bitterly. “So it’ll be the captain of the guard or someone close to him, like last time, so they can break his defensive spells.” After a moment, a hopeful look crossed her face. “Is Shining Armor in on this?”

Lyra shook her head. “No, but he’s in Canterlot. There’s diplomacy ahoof and that’s providing cover for Cadance working with us on this investigation.”

Getting back to her feet, Twilight began slowly pacing around the library, mimicking Lyra’s earlier movements and absently reshelving the hooffull of books that had been disturbed.

“So,” Lyra eventually said as she watched her fellow unicorn’s aimless puttering. “What do you think?”

“I think,” Twilight said thoughtfully, before turning and leveling a dark glare at Lyra. “I think I don’t trust you. How do I know you’re not a Changeling?” Twilight’s horn flared dangerously, and she braced her hooves against the floor

Lyra’s eyes widened and she smiled slightly, seemingly unfazed by Twilight’s implied threat. “Very nice! A good suspicion, but I’m clean. See?” She raised a hoof. Twilight looked, and instead of seeing the normal, healthy soft tissue inside the hoof capsule she saw a little brassy metal plate set neatly into the hoof, pulsing slightly in time with Lyra’s heartbeat.

“Eugh!” Twilight cried, recoiling from the sight and looking away, the light around her horn dying away. “Lyra, that’s disgusting! How could anypony do that to themselves?”

Lyra set her hoof back down and grinned expansively. “It protects my frog and improves circulation. I can run farther and faster and even work in low-oxygen environments. They’re really worthwhile implants!” Her grin then faded. “But you know what they mean, right?”

“You can’t use shapeshifting magic with implants,” Twilight said sarcastically, rolling her eyes. “I know. Which is another good reason not to use them!”

“But it does,” Lyra said, raising a hoof again, “limit our suspects.”

“Oh, sure,” Twilight snapped back. “To anypony smart enough not to get bits of metal stuck in their body. Which is most ponies!”

“Funny you should say that, that brings me to the last bit of bad news.”

Twilight sighed and pressed her hoof against her muzzle. “What now?”

“Your friend Applejack is in danger.”