The Dark Pony of the Night, Mare Do Well is out hunting the musical villain Music Mull who wants to control the whole world with his mind control singing and this number is abut how he feels about Mare Do Well making him and everypony else unwell.
After the mysterious murder of her parents, Twilight Sparkle must don the cape and cowl in an effort to discover the killer. Meanwhile, Discord has set about procuring her a mentor in crime-fighting.