北宋徽宗年间，镇远大将军凌落石与当朝奸相蔡京相互勾结，狼狈为奸，致使朝纲败坏，国势日衰。身兼武林大联盟副盟主的凌落石，更因觊觎武林盟主宝座，而趁盟主冷悔善过寿时，将其杀害，取而代之，冷悔善幼子冷血（蒋毅 饰）侥幸死里逃生，并为太傅诸葛神侯（岳跃利 饰）收养于狼窟中长大。诸葛神侯为对抗武功高强、阴险狠毒的凌落石，除个别传授冷血武功，亦同时培养另外三位极具资质潜力的血气青年追命（钟汉良 饰）、无情（朱磊 饰）、铁手（车仁表 饰）分别授与武功有成后，以分进合击方式，展开连串刺杀凌落石之艰巨任务。四人呗诸葛神封为“六扇门御前四方总捕” ——东方总捕铁手、南方总捕追命、北方总捕无情、西方总捕冷血，四人分别保卫着四方各地安宁。

During the reign of Emperor Huizong of the Northern Song Dynasty, General Ling Lushi colluded with Cai Jing, the traitorous minister of the dynasty, resulting in the corruption of the dynasty and the decline of the country's power. In order to fight against Ling Lok Shek, who is a powerful and vicious martial artist, Zhuge Divine Constabulary teaches Coldblood individual martial arts skills, and at the same time cultivates three other young men with great qualifications and potentials, namely Life Snatcher, Emotionless, and Iron Hands, who are trained to kill Ling Lok Shek by combining and dividing their martial arts skills. The four of them are appointed by Zhuge God as the "Four Chief Constables of Department Six" - Iron Hands in the East, Life Snatcher in the South, Emotionless in the North, and Cold-Blooded in the West - to safeguard the peace and tranquility of all places in the four directions.