By Tim Jackson

Heartwarming themes of love lost and the emotional power of music are undercut by a script constructed for the sake of dramatizing ideas rather than characters.

The Ballad of Wallis Island, directed by James Griffiths. Opens April 4 at The Coolidge Corner Theatre & The Kendall Square Theater

Carey Mulligan and Tom Basden in The Ballad of Wallis Island.

The Ballad of Wallis Island begins with Herb McGwyer stumbling off of a dingy that has shuttled him to Wallis Island, a small isle found north-east of Fiji. His clothes and suitcase drenched, Herb is one half of a formerly popular duo called McGwyer-Mortimer. He is greeted by Charles Heath, an eccentric lottery winner and multi-millionaire. Charming and naïve, Charles leads him to his secluded estate, where he has agreed to pay half a million pounds to the musician for a private concert on the beach for Charles alone. To the singer’s surprise and dismay, he has also hired McGwyer’s former partner and lover Neil Mortimer to join him for an unanticipated reunion. Now remarried, she arrives with her new husband on tow. McGwyer, a hangdog pessimist, is resistant. Apparently, there is emotional baggage he would prefer not to revisit. What that might be is unclear.

This bittersweet tale of love lost unfolds at a leisurely pace. Tim Key, as Charles, infuses his character’s bad puns and double-entendres with the whimsical charm of a super fan. Because he has recently lost his wife,  Charles finds that the music of the former duo holds special meaning for him. For McGwyer, the gig promises to renew the joy he had with Neil years ago. After Mortimer’s husband confides that the couple could use the money, McGwyer agrees to rehearse for a reunion.

Unfortunately, heartwarming themes of love lost and the emotional power of music are undercut by a script constructed for the sake of dramatizing ideas rather than characters.. Tom Basden, as McGwyer, sings and plays guitar well enough, though the songs are not particularly memorable. On top of that, he lacks the charm or charisma to convincingly suggest that he might at one time have been half of a successful folk duo. In rehearsals, Mortimer, played by Carey Mulligan, adds simple harmonies as McGwyer replies with adoring glances. It is a real stretch to imagine that these songs would be enough to satisfy Charles, who also owns a lock of Mortimer’s hair and one of the pair’s guitars.Would he really pay a fortune for a concert this thin?

Akemnji Ndifornyen, as Mortimer’s husband, is conveniently written out of the drama when he heads off to go birdwatching. That leaves the two former folk idols free to sing, moon, and squabble. Unlike two other recent films from the U.K. — Once and Sing Street — a tangible passion for music is lacking. The songs are forgettable and they are rarely sung to completion. Mulligan’s character is underwritten and the two performers have little chemistry together. Basden, in particular, spends too much of his time moping around in fits of anger and frustration.

The character of Amanda, a local small store owner, played by Sian Clifford, is effectively drawn, but she mainly exists for Charles to pine over. This island has no visible harbor and, apparently, no other inhabitants. (I had to look up where this aisle is allegedly located. Does such a place exist?) The locations are reduced to the shore, a few trails, Charles’ island mansion, and a small local store, of which we see only the counter. When McGwyer asks for rice to revive his wet cell phone, Amanda has none on hand  — though somehow it arrives — perhaps by carrier pigeon? Can a phone drenched in salt water — and later dropped in boiling water — really be revived in a bag of rice? Its nitpicking but, like too much of the film, it shows how the narrative is more about unconvincing cuteness than emotional reality.

The film evolved from an earlier short, The One and Only Herb McGwyer Plays Wallis Island, a prize winner at the Edinburgh International Film Festival. That effort was also written by its lead actors (Key and Basden) and directed by James Griffiths. This is a case of misfired expansion: characters have not been developed and a movie about music better have some memorable songs played with flair and enthusiasm. Longing glances, droll humor, and a few temper tantrums don’t do the trick.

Tim Jackson was an assistant professor of Digital Film and Video for 20 years. His music career in Boston began in the 1970s and includes some 20 groups, recordings, national and international tours, and contributions to film soundtracks. He studied theater and English as an undergraduate, and has also worked helter-skelter as an actor and member of SAG and AFTRA since the 1980s. He has directed three feature documentaries: Chaos and Order: Making American Theater about the American Repertory Theater; Radical Jesters, which profiles the practices of 11 interventionist artists and agit-prop performance groups; When Things Go Wrong: The Robin Lane Story. And two short films: Joan Walsh Anglund: Life in Story and Poem and The American Gurner. He is a member of the Boston Society of Film Critics. You can read more of his work on his blog