In Southeast Asia's M country, a border patrol vehicle was attacked, and four soldiers survived. The person who planned this attack is nicknamed the pit viper. On the eve of the attack, the security officer of the oil and gas plant, Zian, was facing a difficult problem. Former comrades Tian Ai and Fei Luo traveled thousands of miles to M country, hoping that Zi'an would return to the martial arts world and accept mercenary missions. But Zi'an is tired of the sword and shadow, and only wants a peaceful life to accompany his fianc é e XiaoYue will never grow old. Just as the three of them bid farewell with reluctance, the special operations team of the pit viper infiltrated the oil and gas plant to install explosives. The three of them rushed to the battle, relying on their excellent individual combat abilities to defeat the first round of attacks by the viper. NitrateAs the smoke dissipated, the viper took advantage of the enemy's cleaning of the battlefield and fired a deadly shot, taking Tianai's life. Tian'ai died in Zi'an's arms. Zi'an's heart was broken and he wanted to die. The viper disappeared like a ghost in the vast mountainsKnowing his whereabouts, Zian finally picked up his gun again and wanted to recover the blood debt for his comrades.