“The Ballad of Wallis Island” tells the of Charles, an eccentric lottery winner who tries to reunite his favorite musical duo Mortimer-McGwyer despite the fact they split up many years ago. Making things even more awkward, the musicians – Nell Mortimer and Herb McGwyer — were also once romantically involved with each other a la Sonny and Cher. 　　One day, Mortimer and McGwyer are summoned to Charles’ remote island to play a private show. As old tensions resurface, Charles desperately tries to find a way to salvage the situation so that he can finally enjoy his dream gig