During the war between Wei and Shu, the Shu defeated the Wei using the crossbows they make. In order to attain this powerful weapon, the Wei sent numerous spies to infiltrate the Shu kingdom and steal it. Chen Gong and Xun Xu are Shu spies who have infiltrated the Wei kingdom for many years. After knowing the plan of Wei, they decided to work separately to stop it. Chen Gong continued to stay in the Wei kingdom, while Xun Xu went back to the Shu kingdom to investigate. In the midst of the investigation, Xun Xu finds out the thief of the crossbows - Mi Chong. He also discovers a highly-skilled spy named Zhu Long who is ambushed in the Shu kingdom, who is waiting for the opportunity to initiate the Qing Ping plan. Xun Xu devised a scheme to hook Mi Chong, using it as an opportunity to destroy the spy network in the Shu kingdom.

Despite eventually capturing Gao Tangbing, a corrupted officer, the real Zhu Long is actually someone else. Chen Gong also ends his spy career in the Wei kingdom, and goes back to the Shu kingdom. Together, Xun Xu and Cheng Gong investigate the Zhu Long incident and discover the truth behind the Qing Ping plan.