Plum parts for film actresses over 50 have always been in criminally short supply, and roles “with legs,” as Susan Sarandon likes to say — with romantic, sexual subtexts — are even rarer.

So the great British beauty Natascha McElhone makes the most of such a unicorn in “Carmen,” a sad-eyed last chance romance set on the scenic isle of Malta. In the title role, she impresses and sometimes dazzles as a downcast local figure of fun, the village priest’s sister who “never smiles and never speaks,” so the locals gossip.

Always dressed in black, always seated at the back of mass, she has been her older brother’s housekeeper since he joined the priesthood. But what’s she to do when he dies?

God never abandons the faithful, the smug bishop tells her, taking care to not use the word “church.” She’s got to move out for the new priest — returning to Malta from abroad — and the new priest’s caretaker sister.

“In prayer you can find your way.”

With no family, no money, no friends and no home, Carmen wanders the streets with her lone suitcase in silence, utterly at a loss. She overhears lover’s quarrels and flashes back to some romantic trauma from her past. She sees the local hooker bow and accept her affectionate catcalls, notes how much the village policeman naps. And she ‘s in the shadows when the new priest’s sister, a local (Michela Farrugia) moves into the rectory, and fights with her lover (in Maltese and English), who wants to take her away from all this.

The lover, the church bellringer, breaks the clapper on the bell as he storms off. And Rita, like Carmen, finds herself alone.

But there are places within the church to hide. A purloined set of keys means she can take a nap in the confessional. When locals duck in, thinking the new priest has arrived, Carmen starts hearing the women’s complaints, darkens her voice (not much), and doles out homespun, blunt advice.

Your dead weight husband won’t leave? “Cook him the same meal, morning noon and night.” The offering box starts to fill up as word gets around.

Carmen may have found her calling. But surely Rita’s going to catch on to this. Eventually.

Maltese actress turned director Valerie Buhagiar (“The Anniversary”) does three things with great elan here. She showcases the beauty of her rocky island home. She gives her leading lady free rein. And she trips up expectations time after time in this quirky 1980s period piece.

A street vendor selling capers from his donkey cart flirts with quiet Carmen with Zorba-like enthusiasm.

“A person can get sick keeping their love to themselves!”

That’s not what the movie’s about, him courting her and leading her back to life. We never see him again.

The whole fake priest in the confessional bit is cute, but more a means to an end. The backstory of a lost love/forbidden love dating from “the war” has more import, but isn’t really the meat of the movie either.

Buhagiar keeps things on the cusp of fantasy as Carmen’s distant past and recent past and simple survival (we wonder how she eats) aren’t fussed over. She just is, and she’s overdue for a makeover. Maybe that cute younger pawn shop operator (Steven Love) in the capital city of Valetta can help.

McElhone mopes in the early scenes and shimmers through the later ones, even as she suffers. “Carmen” becomes a veritable Maltese fashion shoot at times.

But shortcuts and missing details aside, it’s never less than charming and a grand showcase for a busy and beautiful actress whose best roles are on TV (“Hotel Portofino,” “Designated Survivor”) these days.

Rating: unrated

Cast: Natascha McElhone, Michela Farrugia, Steven Love

Credits: Scripted and directed by Valerie Buhagiar. A Good Deeds Entertainment release.

Running time: 1:28