During the Anti-Japanese War, Yun Hongshen unknowingly chases after his father's killer, only to fall into a trap set by "Black Butler," a Japanese spy who had been undercover in China for 15 years. With the help of a close family friend and guidance from the Communist Party, Yun Hongshen joins forces with patriotic youth Wen Yeming to expose the spies hidden within the Nationalist army. Together, they set intricate counter-traps, overcoming personal vendettas to help turn the tide of war.