


Trish interrogates each suspect, but no-one gives in and Chuck is spotted singing Ally's new song that has not been released yet, Kimmy was still hung up that Ally was voted prom queen instead of her, and Trish believes it's Miles as it's always the quiet ones. When the librarian asks Ally what it looks like Ally reveals all her sentimental emotions of the last 17 years and when Dez steps in and states its a brown book with the letter A the librarian reveals she saw someone running with it, they were wearing a big blonde wig and a white jumpsuit and when the awesome foursome hit the dance floor they see Kimmy, Chuck and Miles wearing the same outfits the librarian described the question now was whodunnit?! As the four friends hit the dance floor with some amazing moves they all return to their tables where Ally finds that her songbook is not in her bag creating a real "Whodunnit" the gang visit the school library, leaving Austin amazed there is such a place, they ask the librarian whether she saw someone suspicious or if she saw someone if Ally's book. We see the four friends arriving together as Groovy Goat and the Mystery Bunch (a spoof of the kids from the Scooby-Doo franchise): Austin- supposedly Fred- Ally-portrayed as Daphne- Trish as Velma and Dez as Shaggy! And not to mention Dez's pet goat. Austin & Dez enter acting and looking like they are in their actual 70s, making funny jokes and behaving like elderly men.

The episode starts off with Trish coming into the A&A music factory forgetting her big news and Ally reveals to Trish she had finished a song for her new album, bringing back Ally's original quote "Don't touch my book!" Trish finally realizes that the reason she came to the music factory was to ask Ally what she is planning to wear to the 70s disco party! Ally states that she doesn't know yet, although she does reveal Austin & Dez are very excited about their costumes. The gang goes in search of the culprit, dressed like the "Mystery Bunch." A mystery unfurls when Ally’s songbook is stolen from the school’s ’70s-themed party.
