Grace, Annie and Tommy are growing up fast as police officers, but nothing can prepare them for the turmoil they face every day. It’s a year since the fall of the McIntyre crime gang and the vacuum has been filled by rival gangs, all competing for dominance. Constable Shane Bradley is drafted in to help, but his motivations are unclear. Tommy is dangerously seduced by the world of intelligence policing, while Grace struggles to deal with her son’s absence, and growing feelings for fellow officer Stevie. As a young loyalist threatens to take over the city, the officers face a major gangland feud – culminating in a violent and devastating confrontation.

该片故事改编自布朗纳撰写的文章《追踪弗雷 加德特工》(Chasing Agent Freegard)，讲述一桩真实发生的故事，职业骗子罗伯特·弗雷加德(诺顿饰)是个操纵人心的高手，他让无数受害者相信他是军情五处的卧底，以此敲诈和绑架他们。阿特登所饰的角色最初为他的魅力所倾倒，后来成为了弗雷加德垮台的关键人物，她的行动导致他被定罪和逮捕。

　　BBC宣布一次性续订《警之光》两季。