After the trials of the first two films, Bobby (voiced by Anna Kendrick) and Bran (voiced by Justin Timberlake) are now officially a couple. Just as their relationship is getting closer and closer, Bobby discovers that Bran has a mysterious past. He used to be a member of her most crazy boy band "Brother Zone", which was a boy group composed of him and his four brothers Floyd (voiced by Troye Sivan), John Dory (voiced by Eric André), Spus (voiced by Daveed Diggs) and Clay (voiced by Kid Cudi). But the brother band disbanded when Bran was still a child, and the family was torn apart. Since then, Bran has never seen his brothers again. But when Bran's brother Floyd was kidnapped by two evil villains of pop music, Fanfei (voiced by Amy Schumer) and Fanny (voiced by Andrew Rannells), Bran and Bobby embarked on a thrilling adventure, hoping that Bran and his other brothers could reunite and rescue Floyd from a fate worse than becoming a has-been star in the pop music industry.