One evening at a restaurant, as customers bicker and quarrel, three new characters sing and take in the green substance that has filled the floor. However, one of them isn't thrilled about the results, revealing another of them to be Adagio. She wants something other than fast food but Adagio reminds them that the power here isn't the same and they can only gain so much. She wishes not to have been banished to the human world but Adagio's sarcasm slips by the third member revealed to be Sonata.
A column of light appears and breaks the conversation and once outside the trio discover it's Equestrian magic, which they will use to get everyone to adore them.
With that, the new opening sequence rolls complete with an entirely new song. The next day, we find the students of Canterlot High working on posters of sorts. Sunset Shimmer, now totally good (and better I might add) takes the paint brush, offering to help the Cutie Mark Crusaders with their work.
Unfortunately, the trio aren't interested so SS returns the paint brush to them and Pinkie Pie calls her over but the mere mention of her name has everyone else recalling the past events and not in a good mood.SS didn't realize the whole school would be there and is shown the frosting covered poster that Fluttershy is intrigued by and ends up taking some on her nose and SS finishes the job. Principal Celestia and Vice Principal Luna appear to commend all those entering the upcoming musical, which'll be the best since the fall formal and once again bad memories of the past are triggered, leaving SS unable to cope any longer.
Later, the group have their instruments and recall what happened but the Mane Six forgive SS for what happened before. It's brought them closer than ever before and they explain how with a song where SS ends up grooving along and the band members obtain some of their pony properties. When it wraps up, SS is pleased with the song and the pony add-ons disappear but it isn't clear why they appear in the first place since Twilight took her crown back with her.

Rainbow Dash doesn't care as it makes her band totally awesome but the others are not approving of that in spite that RD came up with the idea for the band. Flash Sentry enters to remark on how good they all sounded but RD has a few nitpicks (and not good ones at that as they sounded great to SS and my ears). When he learns that Twilight is unlikely to return anytime soon, he heads out. Rarity had forgotten that SS and FS used to be a couple but SS only used FS to gain popularity. The important thing is that SS turned around but SS doesn't feel everyone else does (and understandably so given that they don't see SS being nice).

PS calls for SS to the foyer to show the new students around and get to know her new self. While the band practices RD's song, SS begins showing the trio around but mentioning the musical showcase has the trio smirking with delight. Sonata practically blurts out the plans but Adagio keeps things in check.The pendants catch SS' eye and she goes to point them out to ask where they were bought but they're so precious to the trio that they hate for anything to happen to them. As the trio walk away, SS is a bit puzzled and shares her experiences with the others at lunch. Outside, the trio are ready to begin their plan but all Sonata can think about is lunch and is instructed to follow Adagio's lead.

They enter with their own song about a different kind of event taking place. As the song progresses, students are slowly turning on each other and by the time the song is over, the vast majority is now against each other creating the same energy from before. Afterwards, the group realize what's going on and don't need a repeat of the Fall Princess Formal. However, when they mention this to PS and VPL, they don't buy it (not sure why you all didn't record the events) and suggest reasons against their story due to a little encounter with the trio (whose band name is The Dazzlings) earlier (and thus manipulating them into not preventing the events in the cafeteria).

Outside the portal, the group discuss what's happened and why they weren't affected. They need a way to get to Twilight but the portal is closed but SS gets an idea and goes to her locker to retrieve the book she had from when she was Celestia's student. Only thing to do now is to see if the magic still works by attempting to get a message to Celestia then to Twilight from Celestia.

She starts writing and we find the Pony Six in Twilight's new castle where a janitor of sorts is pulling a cart with books piled high, including one with a cell phone vibration. The group watch and wait as Twilight opens the book to learn of the letter to Celestia about Canterlot High. Realizing they need her help, Twilight brings out her book on the Sirens and explains the story to the others. They don't know why the trio is only surfacing now when they were likely banished there ages ago but it must be only the beginning. How will they get a message back with the portal closed? Pinkie Pie gives Twilight an idea and a new portal is created that will allow the transfer of a pony from their world to the human world and back again.