During the Southern Song Dynasty, General Yue Fei led the Yue Family Army in valiant resistance against the Jin invaders, achieving great victories and sweeping all before them.

The Jin army, terrified by his reputation, instigated Qin Hui, who had previously defected to them, to return to the Southern Song court and sow discord between Yue Fei and the emperor.

Eventually, Yue Fei and his son were framed and condemned by Qin Hui.

General Han Shizhong, feeling indignant, confronted Qin Hui and demanded an explanation. Qin Hui famously replied, "Though the letter from (Yue) Fei's son Yun to Zhang Xian is unclear, 'it may exist' regarding the matter." (Original Chinese: 飞子云与张宪书虽不明，其事体莫须有。)