"We have to do something."
There was plenty to be done as it was. All of the changelings had left Twilight Sparkle's body but she was not out of danger yet. Their thorny, chitinous bodies had inflicted considerable internal damage, and the substances surrounding their foreign bodies could cause who knew what infections.
Nevertheless, Dr Horse knew Nurse Redheart was correct. Shining Armor was struggling to fight off the changelings mauling him, Cadance was unconscious, Twilight's friends were trapped, and the other changelings scattered around the operating room floor were gradually beginning to stir. If the surgical team did not take measures to keep the changelings at bay, any repairs done to Twilight's insides would count for nothing.
"Sweetheart, try to revive Princess Cadance. Knockout, cover her. Redheart, number 12 scalpel."
Sweetheart wound her way past the fallen changelings over to Cadance and began forcing air into the pink alicorn's lungs, while Knockout anxiously stood guard beside the pair. Redheart passed the specified blade to the doctor: a long, wide blade, hooked like the profile of an eagle's beak. Dr Horse guided the blade towards Rarity, who was uttering loud groans of disgust at the sticky substance fastening her to the floor.
As soon as she saw the blade gliding towards her, Rarity ceased her complaining. "No Doctor, you must start with Applejack and Rainbow Dash. They are much better at fighting than I." She knew her words might be construed as trying to keep herself out of harm's way, but there were far more important things at stake then her pride.
"If I can loosen your bonds a little," replied the surgeon, "you can help me free the others".
Rarity pondered this for a second. "Splendid."
The sharp blade scythed through the taut silken strips swaddling Rarity's forelegs and withers until she was able to elevate her front half enough to turn to her side. The unicorn mare called for her own scalpel, which she started applying to Applejack's restraints, while Doctor Horse set to work on releasing Rainbow Dash. Although the scalpel was unfamiliar in Rarity's magical grasp, her experience with various cutting implements enabled her to get the hang of the instrument expediently.
Within a minute, Applejack and Rainbow Dash were able to bolt to the other side of the theatre and set upon the changelings anchored to Shining Armor's muzzle. They could not deliver full-force kicks lest they harm their ally in the process. Instead, they clapped their forehooves around the sides of the changelings' heads and wrenched at their thoraxes until the monsters finally relinquished their hold, whereupon the two mares promptly slammed them across the floor then helped Shining rid the changelings from his underbelly.
Not a moment too soon, for the other changelings in the room had picked themselves up in preparation another assault. Shining Armor, Applejack and Rainbow Dash drew close together, their haunches elevated in readiness for battle, while their opponents clattered their translucent wings and hissed aggressively. Each side waited tensely for the right moment to strike.
"HERE I AM!!"
The changelings whipped around as one towards the source of the exuberant, falsetto exclamation. Rainbow Dash took immediate advantage, firing herself like an arrow towards the centre of the changelings and scattering them left and right. Shining Armor, Applejack and the newly-freed Pinkie Pie galloped in to lend some assistance.
A squad of half a dozen changelings took to the air to bombard the ponies, only to find themselves in the trajectory of Fluttershy, who swooped mightily back and forth, swatting and kicking aside any changelings in her path. There was no need for her friends to feign injury this time. These creatures had already hurt Twilight Sparkle on the most profound level. Any concern the enraged pegasus had for her own welfare was gone.
Severing the last of Rarity's bonds, Dr Horse cast his scalpel towards the other beslimed used blades before he joined Redheart in cleaning and mending Twilight's interior. The newly freed Rarity darted gracefully from one melee to the next, landing blows that made up in precision for what they lacked in strength.
United as a team, drawing courage and inspiration from one another, the ponies began to gain the upper hoof. One of the changelings, larger than his hostmates by a small but significant degree, opened the theatre doors and let out a rasping hiss, drowning out the noise of the battle. His siblings turned towards the commanding sound and shot out to the hallway. Rainbow Dash set off in pursuit but she only had time to glimpse some of the retreating changelings assuming the forms of the ponies in the theatre before Shining Armor magically slammed and bolted the doors and stood imposingly in front of them.
"Let them go."
"But they're going to attack Ponyville," Rainbow protested.
A thunderous peal resounded through the operating theatre, alarming all conscious ponies in the room except Shining Armor.
"Not on my watch," he replied as more clanging noises permeated the room.
Applejack beamed behind her mask. "A forcefield."
"They can hammer away at it for a week and not make a dent."
"I wish I could say the same about those doors," warned Doctor Horse, without looking up from Twilight. "This is a hospital, not a fortress."
Shining Armor guided a high-backed chair towards the doors and wedged it under their handles. He then planted his forehooves firmly on the smooth floor and braced his hind legs against the doors. Twilight's friends quickly followed suit, just as the doors jolted under the impact of the returning changelings. Laughing and hissing, the parasites slammed their tough bodies forcibly against the other side of the doors, small groups taking turns so as to maintain a steady barrage. All the while, the resounding blows against the forcefield continued in the background.
As the ponies fought to preserve their barricade, they had their first chance to notice Cadance, now breathing but still unconscious. Sweetheart had placed a cold compress on the pink alicorn's head but further treatment would have to wait until the changeling attack ceased.
"Princess Cadance," cried Rainbow Dash.
Applejack turned her head remorsefully towards Shining Armor. "We're powerful sorry, yer highness. These critters are a tad stronger than the ones we tangled with in Canterlot."
"No wonder. They've been feasting on a deep vein of finest-quality love for days," the captain replied, grim but unreproachful. Another factor at play was the timely intervention of Twilight's friends during that first battle at Friendship Castle. Spinnerette had the time to deposit only a minority of her offspring into Twilight, so those who were able to incubate could consume a greater share of their host's love than they could if part of a full brood. This greatly increased their individual strength. Conversely, the small size of the brood not only saved Twilight's life when she cast her anti-disguise spell over herself, but meant that the changelings were not numerous enough to conquer Ponyville by force, so they would have to rely on their uncanny shape-shifting ability to deceive and drain their prey over a long period.
The relentless assault on the doors began to open a gap that widened slowly but inexorably. The ponies pushed ever more desperately to close the gap until Knockout, eyes gleaming, galloped towards the doors, climbed onto the chair and thrust his horn through the gap.
A jet of soporific gas expanded and flooded the corridor. The changelings instantly collapsed, coughing, wheezing and finally fainting. Two of them frantically tried to flee the vapour. Knockout sprayed ever harder, shouting with effort, until the pair succumbed to the effects of the gas and staggered to the floor. Knockout himself then slumped in the chair, spent. The ponies exhorted him with assorted cries of 'all right' and 'way to go'.
"How long do you think they'll be out?" Shining Armor asked.
"Can't ... say," Knockout panted. "Uncontrolled dosage ... wide area ... creatures of unknown constitution."
"Then let's go in and finish them off." The hovering Rainbow Dash brandished her forehoof aggressively.
"We cain't go in there, Rainbow. The gas could take us out too." Applejack grunted and spluttered as a sudden gust of wind blasted her in the face, blowing her Stetson to the floor.
Rainbow Dash chuckled smugly at the glaring earth pony. "I'm not just a pretty face, you know, AJ." Taking a deep breath, she opened the theatre doors and flew several speedy laps through the corridor, her powerful, rapid wingbeats dispersing the gas. Sniffing the air a few times and deciding it was safe, she beckoned her friends to join her.
Shining Armor, brow furrowed with concern, was the last to join them. "I've just spoken with one of the nurses. They'll have to keep Cadance under observation for a good while yet. We can forget about casting that love wave for now."
Rarity looked around at the dozens of inert changelings littering the floor. "What are we going to do with all these creatures? They could recover any moment."
"Who wants to play dress-ups?"
At the sound of this excited, utterly incongruous suggestion, the other ponies turned incredulously towards Pinkie Pie, only to see that she was carrying a mountain of medical dressings that she had somehow managed to retrieve from a supply cupboard. Smiling, Rarity guided the dressings towards herself and began expertly tying the changelings up.
Fluttershy glanced nervously around. "Um, is this all of the changelings?"
"I think so," replied Shining Armor.
"Then why can I still hear b-b-b-banging against the forcefield?"
The other ponies gasped. In all the turmoil, the continual noise had receded into the background so that they no longer noticed it until Fluttershy mentioned it.
A quizzical frown crossed Shining Armor's face. "Wait a second, it's coming from outside."
"I'll check it out." Pinkie Pie dashed off towards the main entrance and disappeared from the other ponies' view. Seconds later, they listened anxiously as a piercing scream rang down the hallway. As the pink pony raced back, they saw she was not screaming in terror, but squealing with delight.
"You gotta come see this! You gotta come see thiiisss!"
Rainbow Dash stayed behind with Rarity, ready to sound the alarm if the changelings began to awaken. The other ponies followed Pinkie to the hospital foyer, and stared in astonishment at the sight greeting them through the doors that Shining Armor had opened.
Standing at the main entrance, flanked by a squad of bat-winged royal guards, was Princess Luna.