It used to be that for those who found the prickly social criticism of Mike Leigh's movies too chirpy, there was always Ken Loach. With such uncompromising films as Riff-Raff, Raining Stones, and Ladybird, Ladybird, Loach confronted the injustice and pathos of British lower-class life with compassion, complexity, and not much in the way of happy endings. Lately, though, he's expanded his territory beyond the dismay and brimming humanity of the grim burgs of the British Isles for other times and places, and the move has softened his lacerating edge and aching ambiguity into sloganeering.

Such was the case in his foray into the Spanish Civil War, Land and Freedom, and it's a weakness in his charming but ultimately misconceived Carla's Song. Robert Carlyle, in between roles in Trainspotting and The Full Monty, plays George, a Glasgow busdriver with a soft touch and a rebellious streak. Among the impoverished passengers he gives a break to is Carla (Oyanka Cabezas), a beautiful Nicaraguan refugee from the ongoing contra wars who earns her living dancing in the street. Moved as much by her exotic allure as by concern for her welfare, he finds her a place to live, nurses her back to health after a suicide attempt, and learns the reason for her despair -- her boyfriend Antonio (Richard Loza) was captured by the contras and probably killed.

Although he loves Carla, George magnaminously urges her to go back and find Antonio -- he even accompanies her. Released from the gritty accents and gray details of Glasgow, the film dissipates into a bit of a screed, with Carla and Scott Glenn as a mystery American named Bradley providing much of the speechifying. It's earnest but unfortunate -- Carla's Song might been more genuinely tuneful had the pair remained behind to take on the Glasgow public-transport bureaucracy rather than the CIA. At the Coolidge Corner.