Princess Cadance's past is a mystery, especially to herself. After Celestia and Luna sense a surge of Dark Magic in the far frozen north, Cadance and her wife go to investigate along with Rainbow Dash and the other bearers of the Elements of Harmony in order to deal with it, and hopefully uncover the truth of Cadance's hidden past.

Unfortunately, waiting for them is a dangerous new enemy, one with one goal in mind: revenge.