Side-story to Past Sins - Spike almost lost Twilight to a hangmare's noose, but now Twilight is safe and Nyx is a filly again. Normal life is returning. Still, Spike can't ignore the fact that Nyx just isn't the same as he remembers her. Her temper is more volatile, and, when she gets angry, all he can see is the rage-driven Nightmare Moon of legend.
And thus Spike has to wonder: Is Nyx truly reformed, or is she one bad tantrum away from calling herself Nightmare Moon again?
Can Nightmare Moon, reborn without her hate, ever escape her past?
In the aftermath of Past Sins, Twilight and Nyx go through the things from Nyx's castle bedchamber
Can Spike trust Nyx again after her actions almost got Twilight hung?
Can Nyx find acceptance with her extended family during Hearth's Warming, or will she find the holiday hymns are filled with nothing but hollow promises?
These are Nyx's first hours.