In the ever-changing tide of the times, the fates of Chun Xiao, Jin Lan, Lin Kan Shan and Ma Qi intertwined and collided on the secret front, and their stories were closely linked to national security and social change. As new forces in the National Security Bureau, Chun Xiao and Jin Lan launched a 21-year-long battle of wisdom and courage with Lin Kan Shan, code-named "North Wind". In a series of major cases related to national security, Chun Xiao and Jin Lan grew from fledgling novices to determined secret front fighters. They unwaveringly cracked down on espionage and defended the country's secrets and security, while Lin Kan Shan and Ma Qi gradually lost their way in the political whirlpool. As time went by, Chun Xiao and Jin Lan guarded the unity of the motherland and the tranquillity of the country at the cost of their youth and blood.
