When Fluttershy went to bed, she was a normal mare. When she woke up, she could see numbers floating over everypony's heads. They were timers, each one counting down to some unknown event. Most ponies had timers that wouldn't end for years, some for many decades. But everypony had different numbers.

So why does Rainbow Dash's timer end in three hours?

Editing provided by TheMaskedFerret and SolidFire.
Cover art by HopefulSparks!
Spanish translation by SPANIARD KIWI!