June, 1867: Idaho Territory. An abandoned, wounded traveler comes across what has to be the biggest mare in the world. Both human and equine are searching for something -- and without each other, neither may ever find it. Or survive...
Princess Twilight Sparkle writes pony history by opening a portal to another world and making first contact with extra-Equestrian intelligence. Only snag: the portal opens at a pony ranch on Earth.
Celestia lands on Earth as a common Arabian mare. Without magic, speech, not knowing the language, she seeks her way home. First though, she needs to make some friends and restore her freedom.
In an experiment gone awry, a pony is brought to Equestria. A perfectly ordinary pony. One so ordinary, it runs the risk of destroying Equestria's very lifeblood.