Luna walked into her chamber, exhausted. "Sister, it is time for you to raise the sun. We have lowered the moon for you already."
Her voice echoed in the silent chamber, empty save for the princess of the night. "Sister? Tia? Where have thou gone?"
Silence. Not that there could have been any answer, for there was nothing else capable of speech in the room.
Luna was surprised, but this wasn't too unusual. It had happened once or twice before, that her sister had fallen asleep in another room instead of going to their shared bedchamber, but she had woken up in time to raise the sun, luckily.
Ah, she should wake up soon, if she hasn't already. Luna figured as she floated her crown and shoes to the floor by her bedside. The princess took a glance at the night sky outside the open window. There was no reason to panic. Celestia was okay. But why did she have such a bad feeling in her stomach, like something was terribly wrong?
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Argh, how could I have done this again? I'm lucky last time nopony noticed and my dignity was saved, but now I have to raise the sun, and somepony's sure to find out. Ugh! Celestia paced back and forth by the doorway out of the castle's basement, shaking her head in frustration. Well, at least I'm safe and not hurt, she thought, trying to be optimistic.
How could she have even locked herself in? She didn't remember closing it behind her, but maybe her memory was just failing on her. Celestia flopped onto the cold ground to wait it out. Surely she would be found and let out soon.
A few minutes passed, and still nothing. Those minutes turned to hours, and soon the scheduled day was nearly over. The sun princess banged on the door with her hooves, hoping somepony was there to hear her, but there was only silence.
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The same silence in Luna's room as she awoke at the usual time that she had to raise the moon. She stretched, and saw the bed next to hers still empty. If Celestia had already lowered the sun, she would have woken her sister afterwards. The blue alicorn began to freak out.
The guards! They should know what happened to my sister! Luna reasoned. The Solar Guards stay with Celestia all the time, they should know if something was wrong.
With barely a moment's hesitation, Luna burst out the door and ran down the hall, completely forgetting to raise the moon.
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By now, Celestia had given up hope. She leaned against the door, tired and hoarse from yelling and kicking at the door. It was an empty hope to think that anypony could come save her now. It had been well over 12 hours now, with no food and no rest. With the last bit of energy left in her, she lifted a golden shoe-clad hoof to strike the metal door. It barely made a sound.
The princess closed her eyes.
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Meanwhile in the rest of Equestria, Ponyville to be exact, everything was in chaos. It had been nighttime for nearly 24 hours, and once the ponies had awaken and seen the darkness, they, of course, freaked out.
Shouts of "Where is the princess?" and "What's going on?" were all to be heard in the usually peaceful town. Everypony was panicking, especially Applejack, Rainbow Dash, Pinkie Pie, Rarity, and Fluttershy. Twilight was nowhere to be seen! They thought that some evil force must have taken them both, and were really worried.
Rarity responded by fainting. Applejack and Rainbow Dash were talking hurriedly in hushed tones. Fluttershy was shivering in a dark corner as Pinkie Pie's hair deflated. They each had their own ways of coping with this assumption that their friend could be in danger, hurt, or worse--dead.
However, there was nothing to be done. Panicking brought nothing. What they didn't know was that Twilight was actually perfectly safe and unhurt. What they didn't know, they didn't want to know...