《执法者们》展现了警廉律三大执法部门合作，以不同使命、但同样的正义之躯与黑暗势力殊死搏斗。警方高级督察周俊杰在追查犯罪集团首脑戴祖福的过程中，经历了挚爱牺牲、同僚背叛的重重打击。廉政公署高级调查主任高浩然在追查内鬼的过程中，不断在亲情、正义之间挣扎，而律政司副刑事检控专员刘宇凡则在法理与人情之间寻求平衡。执法者们在迷雾重重的权力游戏中，抽丝剥茧，最终将罪恶绳之以法。该剧以紧张刺激的叙事节奏，刻画了人性的复杂与斗争的残酷，彰显了公平正义的永恒价值，并反思了执法过程中人性与权力的博弈。
As Leo's replacement Thomas Chamberlain arrives Nikki investigates the murders of Rachel Freedman, shot in the head, and her little autistic son Nathan, who was poisoned. Nikki rejects policewoman Anne Burchett's theory that Rachel killed them both but is perturbed when an impostor, claiming to be Rachel's sister, visits the morgue. At the same time the disfigured corpse of Eva Liron is discovered, killed with the same poison as Nathan. She had been the nanny to French hot shot footballer Isaac Dreyfus and was planning to blackmail him over a sex tape of them both. Jewish Isaac is a controversial figure due to his anti-Muslim sentiments but he denies ant part in the murders. Then another victim, Isaac's agent Mousa, is discovered dead.
新一季将延续第二季的故事，自Rachel Carey（荷丽黛·格兰杰 饰）在全国直播中揭露一段伪造的政府部长视频、暴露情报机构秘密操作项目“修正”以来，已过去一年。在对“修正”计划非法使用的调查期间，Carey成为SO15反恐指挥部的代理负责人，试图通过全新的“真相行动”摄像系统重建公众对监控技术的信任。然而，一场精心策划、极其残忍的恐怖袭击突然爆发，直击英国权力核心，仅留下一位目击者。随着Carey深入调查，她被卷入一场不断扩大的地缘政治危机之中，这场危机渗透至英国政坛、安全机构乃至媒体界。一场巨大的阴谋正悄然展开，但幕后黑手究竟是谁？
格林和他的新搭档乔·丰塔纳调查了一名伊拉克战争老兵被谋杀一案，这名老兵有更多阿布·格莱布监狱的照片。一名伊拉克妇女是美国公民，她被指控，但她声称自己是一名战俘。
