Twilight Sparkle woke up in the caves below Canterlot. “Ow. My head.” She took a look around the area and saw crystals everywhere.
‘How did I get here?’ Twilight wondered.
She remembered the wedding rehearsal, her brother disowning her, her friends cutting their ties, and her mentor threatening to send her to the moon. She also remembered Princess Cadence encompassing her in green flames.
“Now I remember,” Twilight said.
Rage flew across her face as she thought about how Cadence betrayed her. She heard maniacal laughter in the distance. She looked at the crystals and saw Cadence’s image on them.
“You just had to be nosy,” Cadence mocked. “Oh, I’m Twilight Sparkle. I helped shun three fillies for idle gossip, I’m jealous that my brother is marrying somepony else. I so smart that I'm don’t even need friends.”
Twilight glared at Cadence. “How did you know about the gossip?”
“What?” Cadence appeared on another crystal. “Just because I’m getting married doesn't mean I can’t read the newspaper, Ex-Canterlot Snob!”
Twilight blasted the crystals with her magic. “You ruined my life!”
Cadence appeared on another crystal. “Ruin your life? Moi?” She laughed again.
Twilight’s face grew a bright magenta and then a searing scarlet. She blasted the crystals over and over again.
“I’ll find you,” Twilight raged, “and when I do, I’m gonna make you rue the day you met Shining Armor.”
Cadence appeared in another crystal. “Only way to stop me is to catch me.” She vanished.
She appeared in more crystals. Twilight said, “Fine then. Have it your way.” She started blasting the crystals, but Cadence appeared in more of them.
“Too slow,” Cadence taunted.
Twilight blasted a crystal.
“You’ll never kill me if you can’t find me,” Cadence said.
Twilight blasted another crystal.
“Whatever happened to your fire? Your ice? Your rage?” Cadence said.
Twilight blasted another crystal.
“They’ll never find you here,” Cadence said. “These mines under Canterlo, were abandoned and forgotten years ago.”
Twilight followed the voice and saw Cadence on every crystal there. The multiple Cadences said, “Strike me down with all your hatred!”
Twilight concentrated on the crystals and charged her magic. After a few seconds, she let loose a flurry of fury. Her blasts hit every crystal in the chamber. When the dust settled, she saw Cadence in the flesh.
Dawn approached as Applejack exited her guest room. She remembered yesterday’s rehearsal as the spell Cadence cast on her waned. She felt betrayed again. She wondered what Twilight’s reasons were for this. She put on the dress for the wedding.
She thought, ‘First Apple Bloom, now Twilight?’ She wondered if her other friends and family would betray her. She thought back to her response and realized that she wasn't any better.
She remembered the good times she had with Twilight. She decided to find Twilight after the wedding.
Fluttershy was preparing her birds for one last rehearsal. She was already dressed for the wedding.
“Alright everyone,” she said, “time for one last rehearsal.”
She began conducting. The bird were singing on-key as the spell cast on her faded.
She remembered the previous day’s wedding rehearsal. She looked back to her response and wondered where Twilight was.
The birds had finished their song. But Fluttershy hadn’t noticed. She said, “You were wonderful,” and left.
“More wonderful than me.” She wondered if she was too cruel with Twilight.
She remembered what happened the last time she didn’t take Twilight's worrying seriously.
She led the birds to the wedding hall. She was unsure of what to do.
Pinkie Pie sulked around the reception hall while Rarity helped with the decorations. Their spells had worn off.
Rarity looked outside and saw storm clouds in the sky. “That’s odd,” she said. “Pinkie, when did these clouds appear?”
Pinkie Pie looked out the window. “Dunno, but they’ve been here since yesterday.”
Rarity hoped that the clouds weren’t the windigos. She looked back at the rehearsal, and her response to Twilight's accusations. She thought, ‘Well, if these clouds are what I think they are, then I hope this barrier holds.’
Pinkie Pie looked back at the rehearsal. She wondered if she did the right thing.
Suddenly, her tail started to twitch like crazy. She looked around to look for falling objects, but everything was secured into place.
“Rarity,” Pinkie said. “Do you see if anything’s about to fall?”
Rarity saw Pinkie’s tail was twitching and looked around. But she didn’t see anything that was poised to fall.
The two mares galloped outside to check the rest of the castle.
As the mares left, there was a small crack in Shining Armor’s barrier.
Rainbow Dash was flying around the area. She looked at the skies above Canterlot and saw the storm clouds.
Gale Force was nearby and approached them. She flew to him.
Gale noticed Rainbow Dash and said, “Something wrong, sir?”
“Yeah.” Dash pointed up to the clouds. Gale noticed something familiar about the clouds. “I’ll have my team investigate, but you should warn the others just in case.” He flew away.
As Gale left, the spell on Rainbow Dash broke. She remembered the rehearsal. She remembered how she responded to Twilight’s accusations. She went to the wedding to warn the others.
Princess Cadence wondered what the blast was. She wondered what happened to the wall.
As the dust cleared she saw Twilight Sparkle standing on a now opened area.
Cadence felt relieved, until she saw the look on Twilight’s face. She saw rage, and fury, and wrath. She saw the eyes of a killer.
“Twilight?” Cadence said.
Twilight charged Cadence. But she missed.
Twilight said, “There you are, witch!”
Cadence realized that her captor had also took her form. “Twilight, wait--”
Twilight let out another burst of magic, but she missed. She said, “You cast a spell on my brother,” --she teleported behind Cadence.-- “turned my friends against me, and trapped me in this mine.” She began charging her magic, ice crystals formed around Twilight.
“Twilight,” Cadence said, “that wasn’t me! Someone took my form and trapped me here.”
“Lies!” Twilight said. “You made the fatal mistake of being here.”
The area around them began to freeze over.
Cadence had to do something,or they’ll both perish. She had an idea. “Sunshine, sunshine, ladybugs awake,” --She did the appropriate gestures.
Twilight remembered the first time that she met Cadence since they’d been in Canterlot, she remembered that Cadence didn’t recognize those gestures. She stopped her spell.--
“Clap your hooves...” Cadence said.
“...And do a little shake.” Twilight finished. She realized that the Cadence at the wedding wasn’t the real Cadence.
“It is you!” Twilight said. “But how, why? What happened?”
Cadence started to explain. “It all started when Shining Armor proposed to me. We were dating for a couple months. You cannot believe how happy I was. But that night, I was foal-napped by Chrysalis.”
“Chrysalis?” Twilight asked.
“The changeling queen,” Cadence explained. The two began to find a way to escape the mines while Cadence continued her explanation. “She wants to take Shining Armor’s love and use it to take over Equestria.”
“But why?” Twilight said.
“The changelings feed on love. She figures that with me trapped here, she could use me to feed her army, but she couldn't feed on my magic, so she decided to disguise herself as me and use the wedding as a cover so that her army can infiltrate Canterlot.”
The two saw a cavern. Twilight said, “Do you know about the barrier?”
“What barrier?” Cadence asked. She flew across the abyss while twilight teleported.
“Well,” Twilight said. “Shining Armor had to erect a barrier because a threat has been made against Canterlot. He thinks that the windigos are behind it.”
“But the windigos were slain a thousand years ago,” Cadence said.
“Not all of them, apparently,” Twilight said.
The two continued to find a way to escape while Twilight told Cadence what happened in the previous few days.