A recurring nightmare convinces Luna that, since her return, she has never regained her sister's complete trust. And at the forthcoming Festival of the Eclipse, she decides to make amends with a bold gesture: she removes the moon from the sky.
Princess Luna is slowly recovering from her thousand year exile. Meanwhile on another world entirely Princess Elspeth of Valdemar is trying a new sort of portal spell, which will eventually turn Luna's world upside down.
In the distant future of Equestria, Luna is recalled to Canterlot against her will to participate in a court case that will decide the future for sentient machines in Equestria.