The world of Equestria is inhabited by a multitude of creatures, each possessing their own unique traits and abilities. However, there exists a separate dimension - one where humans reign as the dominant species. Unbeknownst to the public, a portal exists between these two realities - a mirror which connects time with all of space. While monitoring said domains, Luna discovers things are not what they appear, for evil has taken hold in the hearts and minds of humanity. Under the princesses' watchful eyes, Twilight is sent through to uncover the truth of its origin. What she unveils will forever change the course of both worlds' futures.