In 1980s Dublin, 14-year-old Conor (Ferdia Walsh-Peelo) is looking for a break from a home strained by his parents' relationship and money troubles, while trying to adjust to his new inner-city public school where the kids are rough and the teachers are rougher. He finds a glimmer of hope in the mysterious, über-cool and beautiful Raphina (Lucy Boynton), and with the aim of winning her heart he invites her to star in his band's music videos. There's only one problem: he's not part of a band yet. She agrees, and now Conor must deliver what he's promised - calling himself "Cosmo" and immersing himself in the vibrant rock music trends of the decade, he forms a band with a few lads, and the group pours their heart into writing lyrics and shooting videos