Hearths Warming Eve celebrates the unification of the Pony Tribes into the harmonious nation of Equestria. The holiday has long been one of reconciliation, happiness, and unity. However, not all ponies revel in this celebration. There are some among each of the races that openly detest unification, and even go so far as to take up arms for their own independence. This year, in the wake of Discord's return and re-imprisonment, one of these groups sees the opportunity to make their name known to the world. Cobalt Crescent, a veteran agent of the Royal Inquiries Bureau, must leave the family he rarely sees to hunt down these terrorists, and stop a plot that threatens to shake the foundations of Equestrian society in more ways than one.