Twilight Sparkle was suddenly in a dark place, she looked around, "Hello? Is anyone there?" she asked.
She heard laughter echoing around her.
"Where am I?" she asked
The laughter came again, along with a voice this time and a face in the crystals on the walls of the cave that became visible and the cave was lit up. A voice and face that belonged to Princess Cadence, the pony responsible for Twilight being there in the first place. "The caves beneath Canterlot, once home to greedy unicorns who wanted to claim the gems that could be found inside. And now, your prison," Cadence answered.
"Help! Help!" Twilight shouted as she started to run to the other side of the cave
The Princess laughed again her face appearing on a different crystal, "It's no use. No one can hear you. And no one will ever think to look for you, either. Most ponies have forgotten that these caves even exist, which is why they are the ideal place to keep the ones who try to interfere with my plans," she said.
"Plans? What plans?" Twilight questioned.
"Why the plans I have for your brother, of course," she said with nonchalance.
"You better not do anything to my brother you . . . you monster!" Twilight screamed.
The Princess only responded with a laugh and said, "The only way to stop me is to catch me!"
Twilight decided that the best course of action would be to shoot lethal beams of magic at the crystals that the Princess's face appeared upon. And because the only thought that was on her mind at that time was to save her brother, she didn't think about the fact that the Princess in the crystal was only an image.
As the image of Princess Cadence moved from crystal to crystal the Princess's voice laughing and mocking Twilight the whole time, there was finally an instance where Twilight blasted a large crystal near the ground that lead to a different section of the caves where Princess Cadence could be seen, the REAL Princess Cadence with a dirty and matted mane and coat. But because twilight was set on killing the Princess before she could hurt her brother she was all ready to charge in and blast her to pieces.
"No! Wait! Please don't hurt me! Twilight, it's me! Please, you have to believe me," Cadence begged, "I've been imprisoned like you. The Cadence who brought you down here was an imposter," she cried.
"A likely story!" Twilight said.
Cadence started to do their secret greeting song to prove to Twilight that she was the real Cadence, "Sunshine, sunshine, ladybugs awake. Clap your hooves . . ." but she was cut off
"That proves nothing!" Twilight exclaimed, your probably just the impostor trying to give me a false sense of security, after all both the real Cadence and the impostor know that song and dance!" Twilight got this excited look on her face and her horn started to glow as she charged her spell. "I'm going to kill you and save my brother!" she said as she took the shot, unknowingly killing the only chance at saving herself her brother, and everyone else.
Up above in the castle, Queen Chrysalis of the changlings, posing as Princess Cadence, and wife of Shinning Armor, knew that her day had been just perfect.