Princess Celestia is growing increasingly concerned for her sister. Princess Luna's reclusive habits have been getting worse, and she refuses to let herself be helped. Not knowing which way to turn, Celestia enlists the one pony whom she feels can once again reach her sister through the power of friendship: Twilight Sparkle.

Unbeknownst to everyone, something sinister hangs within reach, seeking to cast a thick shadow over all of Equestria. Both Twilight and Luna must come to terms with their feelings of self-doubt and regret before it's too late, and maybe, if they can come to terms with some other feelings, they'll be able to find something even more than friendship along the way.