When Celestia asked the Guardians of Harmony to help reform Discord, they didn't get the chance. After less than a day of freedom, the chaos lord vanished. A year later, the Guardian of Kindness vanished, too...

A year ago, Chrysalis invaded Ponyville and Canterlot with Discord at her side. After a bloody battle resulting in the deaths of countless ponies, Discord was defeated and Chrysalis fled with her changelings. Now in a Canterlot dungeon, the chaos lord is a shadow of his former mischievous self. Despite his betrayal, Princess Celestia strives to understand what drove him to ally with the changelings. Enlisting the help of her sister, Princess Luna, the ruler of all Equestria sends her right-hoof mare to try and ferret out what could've caused Discord to betray them once again.

Deep in the dungeons of Canterlot, Luna engages in a half-mad game of Twenty Questions with the draconequus, desperate for answers. But the more time she spends with Discord, the more questions she has. Why did he help Chrysalis invade Canterlot? Why does he want to kill her now? Who was Rosedust? Why are the Princesses of Equestria responsible for her death and the death of someone else Discord is hungry to avenge? And is all of this an elaborate lie to trick Luna and Celestia into setting their old friend-turned-enemy free once more?