A jagged, fierce drama, “Blue Lights” follows three callow probationary cops in Belfast, in bleak suburbs blighted by sectarian troubles. Partnered with a motley lot of experienced mobile officers with varying degrees of cynicism and toughness, the three recruits butt up against ingrained mobsterism, official incompetence, and uncercover interference. The three core actors—Sian Brooke, Katherine Devlin, and Nathan Braniff—are exemplary, but the complete ensemble is equally impressive. A large proportion of the six episodes dwell on the interiors of squad cars or the police station, and both attain solidity with excellent cinematography. A twisty plot knits the episodes together into a truly epic climax that satisfies in so, so many ways. Gritty, uncompromising, yet full of heart, Blue Lights is a cop show with a wonderful difference.