South Korea's secret nuclear weapons mysteriously disappeared, and at the same time, a plane carrying a military portable device crashed in China. The South Korean side received news that a dangerous person suspected to be nicknamed "Equator" (played by Chang Chen) and his assistant "Messenger" (played by Janice Man) would carry out a secret arms deal in Hong Kong. South Korean weapons expert Choi Min-ho (played by Ji Jin-hee) and agent Park Woo-cheol (played by Choi Si-won) were ordered to investigate. Hong Kong's Counter-Terrorism Special Service Group Director Li Yanming (played by Nick Cheung) and Inspector Fan Jiaming (played by Shawn Yue) assisted the South Korean side in finding weapons, and nuclear physics professor Zhao Zhiren (played by Jacky Cheung) was also invited to assist in the judgment of the case. The weapons were quickly recovered, but unexpectedly there was still a potential crisis hidden. Just as the Hong Kong and South Korean police decided to return the weapons to South Korea, a senior executive of the Mainland Security Bureau (played by Wang Xueqi) and his assistant Miss Yuan (played by Feng Wenjuan) suddenly appeared, and the three parties were caught in a circle. It turned out that there was someone else in "Equator", and their conspiracy began to be implemented...