A long time ago, Discord created a machine meant to plunge the world into perfect chaos. Now, after countless millenia, its cogs begin to turn. Only Derpy Hooves, the least likely pony in the world to stop it, has any chance of stopping it at all.
In Whitetail Wood, there lives a creature of legend. Few ponies have seen it; still fewer believe it to be more than a myth. Sassy Saddles, however, will come to believe.
Weary of the same celebration year after year, Celestia and Luna summon the Grinch and Ebenezer Scrooge to help them put a stop to Hearth's Warming. They regret this decision.
Princess Luna insists that Derpy's nightmares are ordinary. If that's so, why is one of them chasing her into the waking world? For that matter, why has the waking world's Ponyville turned into an evil version of itself!?
Spike still wonders who his real parents were. By coincidence, Derpy Hooves finds out, but the whole experience leaves her with a question: Does Spike need to know?
Derpy doesn't care for Hearth's Warming, and this delivery for Chrysalis isn't helping, at all. The last thing she wants at this time of year is to examine her own heart, but faced with the changeling queen, how can she not?
Derpy has to make a special delivery to Princess Celestia. Little does she know that before it's over with, she'll run afoul of pirates, question her own conscience, and even sit down to a nice cup of tea.
Sweetie Belle notices that Rarity has been acting strangely, and asks Applejack to investigate. Rarity reveals that she has recently received some life-altering news.