When Starlight Glimmer refuses Twilight's offer of friendship, only quick thinking from Spike saves them from being stranded in an apocalyptic future. Fed up with their cat and mouse game, Twilight Sparkle decides to go back to the day Starlight lost her only friend and set things right. The consequences turn out to be more severe than she could have imagined.

Now, trapped together in a dead-end timeline, Starlight's mind is fracturing from the effects of the spell, and she'll have to work with Twilight to put the world back to normal– if only so she can finish what she started.