While performing an inspection of Tartuarus for Princess Celestia with her friends, Twilight is paying homage to one of Equestria's greatest foes: The Lich known as Dead Horse. Upon arriving, they find the Cerberus dead and all the signs that Dead Horse has escaped. Princess Celestia summons her allies; but she finds that even the combined power of Discord, Shining Armor, and all four Princesses cannot defeat Dead Horse. She accepts that, with the Lich using her own ancient magic against her, only the Rainbow Powers can defeat him. As Equestria falls to the undead armies, Twilight springs a trap in a desperate attempt to bring Dead Horse's attack to a close.

After Applejack leaves to deliver a wagon of apples, she stays gone for the whole day. Twilight finds her covered in slime and unconscious on the farm the next morning. When they awaken her, she is gripped with a fear they have never before seen in her. She proves unable to complete the delivery until she consults with her friends, including Zecora, regarding what happened in the Everfree Forest. Told from Apple Bloom's perspective as she watches the ever-strong sister crumble before her, only to be built back up again.

The Summer Solstice is fast approaching, and everypony is gearing up for the annual celebration. But everything is threatened when Braeburn arrives in Ponyville with terrible news. A swarm of Cries O'Melody Beetles is sweeping across Equestria. It is eating all the vegetation everywhere it goes. And according to Twilight, no such swarm has ever been stopped by ponykind. But another erudite pony, Bookkeeper, suggests that Hedgehogs may be the key to stopping the advancing swarm. Twilight, Fluttershy, and Bookkeeper venture into the Everfree Forest to acquire a sounder of their own, save Equestria, and keep the celebration on track.