During the Shaoxing period of the Southern Song Dynasty, four years after Yue Fei's death, Qin Hui led his troops to negotiate with the Kingdom of Jin. On the eve of the talks, the envoy of the Kingdom of Jin died in the prime minister's residence, and the secret letter he carried disappeared. By chance, the soldier Zhang Da (played by Shen Teng) and the deputy commander of the personal guard camp, Sun Jun (played by Yi Yang Qianxi), were caught up in this huge conspiracy. Prime Minister Qin Hui (played by Lei Jiayin) ordered the two to find the murderer within one hour. With the in-depth investigation full of crises, He Li (played by Zhang Yi), the chief steward of the Prime Minister's Mansion, Wu Yichun (played by Yue Yunpeng), the deputy chief steward, and the dancer Yaoqin (played by Wang Jiayi) were involved in the case. There seems to be a bigger conspiracy behind the case. There are bureaus within bureaus, and people's hearts are unpredictable. The situation changes overnight, and the forces of all parties are surging...