由于总统在缅甸遭受恐怖袭击，所以国防部决定对朝鲜进行报复行动，该行动由国防部长崔英灿主导，但21名特种部队成员完成任务后却遭灭口，在好友朴武烈保护下，李震彪（金相中 饰）成了唯一的幸存者。面对国家背叛，他决定复仇。他抢走了朴武烈的独子潜逃至泰国，抚养他长大。28年后，从美国MIT学成归来的李润成（李民浩 饰），带着义父复仇的旨意回到韩国。为了掩人耳目，他的身份是青瓦台国家通信网特聘专家，阴错阳差结识了青瓦台警卫员金娜娜（朴敏英 饰），后者身世凄惨，但颇为坚强，相似的命运让两人发生了一段生死之恋。李润成在复仇时用了“城市猎人”的代号，成为首尔检察官金英株（李俊赫 饰）一直追逐的目标。在一个个消灭主谋的同时，真相正在浮出水面……In 1893, 21 South Korean soldiers were deployed in a secret mission to eliminate some North Korean officers. Yet, halfway through the mission, the South Korean government decided against it and had the soldiers eliminated. Lee Jyn-Pyo was left as the sole survivor and swore to get revenge for his fallen comrades. To do so, he raised and trained the son of one of the soldiers that died who was also his best friend. 28 years later, that boy now a man, Lee Yun-Seon, arrives in Seoul to infiltrate the government and find out the identity of the 5 politicians that gave the elimination order. Yet matters start to complicate themselves when, despite Lee Jym-Pyo's orders to remain detached from people around him, Yun-Seon starts caring for Kim Na-Na, one of the Security Agents for the government.