Twilight and Adagio are very different people. In fact they have almost nothing in common. Except one, very important person: Sunset Shimmer. And despite her best efforts, Sunset has no clue how to make their relationship work out.
Rainbow Dash is troubled. Something eats her from inside, and it is slowly impeding in her friendship. If only she knew what it was. She'd better find it before she snaps at somepony she care about.