The Ballad of Wallis Island follows Charles (Tim Key), an eccentric lottery winner who lives alone on a remote island and dreams of getting his favorite musicians, McGwyer Mortimer (Tom Basden & Carey Mulligan), back together. His fantasy turns into reality when the bandmates and former lovers accept his invitation to play a private show at his home on Wallis Island. Old tensions resurface as Charles tries desperately to salvage his dream gig.