With Sombra threatening pony and changeling alike, Chrysalis and Celestia begrudgingly agree to an alliance. Neither is happy at first. Yet, as they work together, they discover lasting peace, and perhaps more, is possible.
Twilight, Rainbow and Applejack travel 3000 years into the past with their new friend the Doctor, to the ancient city-state of Roan. They meet the famous Leonard DiHoovsie, and find themselves embroiled in a deep mystery with dark implications.
After the harrowing events of "Traveller," the Doctor is forced into having some downtime in Ponyville while the TARDIS rests. Meanwhile, Twilight goes to confide in her beloved mentor, but ends up learning far more than she expected.