本剧由四宗发生在香港，扣人心弦的真实刑案，带出四个令人惊惧的罪行。藉由一队重案组的警探办案实录贯穿而成，包括耸人听闻的「屯门色魔强奸案」，喧腾一时的桃色纠纷「溶尸案」，使市民提心吊胆的「大圈仔军火械劫案」，及「淫业大厦扫黄行动」案件，生动地描绘各阶层犯罪的人性丑恶。而编剧为了加强剧中人物与案件的关连性，特别穿插男女主角CID张兆军（林嘉华）、女CID丁兰（蓝洁瑛）、重案组总督察方伟（陶大宇）、扫黄组女总督察刘婉仪（梁婉静）及聂志华（张国强）一段微妙的五角感情关系，交错编织成属于都市人性化的实录档案。
This 7-year series chronicled the adventures of the Impossible Mission Taskforce (IMF), a team of government spies and specialists who were assigned "impossible missions" by the unseen "Secretary". Although the cast varied over the years, the main characters included The Team Leader (Dan Briggs the first season, then Jim Phelps the other six), The Techno-Wizard (Barney Collier), The Strongman (Willy Armitage), The Master of Disguise (first Rollin Hand, then The Amazing Paris), and The Femme Fatale (Cinnamon Carter, Casey, Dana Lambert, Mimi Davis). The series is best known for its opening mission assignment (conducted by a pre-recorded tape), the theme composed by Lalo Schifrin, the leader's selection of mission agents from a dossier, the opening briefing, the intricate use of disguises and a typical "mask pulloff" scene near the end of most episodes, and the relative lack of characterization of the characters.
