CARLA’S SONG is a superbly performed and moving if regrettably somewhat frustrating movie, released in 1996, barely seen outside film festivals (whispering 305th place in the US box office). Written by Paul Laverty (Bread and Roses), it was his first in a line of pointed social-issue collaborations with Ken Loach, a fearless director unafraid to poke at hornet’s nests of class and conditions that the powerful would prefer left alone. Like their closest American counterpart, John Sayles, the bold yet sensitive duo of Loach and Laverty tackle large themes by focusing on impacted individuals and relationships. People and problems: caring about the former, addressing the latter.

Glasgow, Scotland, 1987. City bus driver ‘George Lennox’ (Robert Carlyle) intervenes one day when a female passenger without a ticket is harassed by a transit inspector. Helping her evade trouble, intrigued by her persona and situation, he discovers ‘Carla’ (Oyanka Cabezas) is a refugee from Nicaragua. After their evolving relationship takes a serious turn, he impulsively buys them tickets back to her country, so he can better understand and she can hopefully resolve the scarring grief that torments her. George is smitten and willing, but the reality on the ground in her spirited but ravaged homeland makes for a brutal education in cause & effect.

Laverty’s debut screenplay was based on his three years spent in Nicaragua, documenting Contra atrocities (Reagan’s CIA-guided “Freedom Fighters”), his script fitting the sweet and tentative fictional romance into a real-life horror story, the Rape of Central America. Unlike the seasoned and cynical journalists of Salvador and Under Fire, George’s earnest, naïve working stiff is unprepared for a world he barely knew existed, and Carlyle’s acting is faultless. But the bracingly honest and winning Cabezas is the broken but still beating heart of the piece. The 24-year-old dancer learned sufficient English during the making of the film, and her own experiences in Nicaragua are achingly reflected in her performance: that emotionally churning delivery isn’t ‘acting’ but inhabitation. Her smile lights up the screen, her tears bruise your heart.

The downside to the gutsy acting, rugged location shooting and the important statement about the human cost of political chess moves is that during at least half of the time focus is undercut by the bad choice of woefully insufficient subtitles, which render a good deal of the dialogue, especially in Scotland, barely understandable. When the plot shifts to Nicaragua, it improves thanks to subtitles of the Spanish speakers, but even that is scattershot. Perhaps the idea was to give the viewer an “immersive” feeling, and that’s what you need to accept, since, unless you’re a native of Glascow and/or fluent in Spanish, you’re on your own. Irritant aside, a vital and affecting film.

With Scott Glenn, Gary Lewis and Richard Loza. 125 minutes.