One day, during the Qianlong period of the Qing Dynasty, the body of Mr. Wen, who was running a restaurant in Gyeongseong, is found dead. Upon arriving at the scene of the incident, Wang Seong-rim, a mailman from Suncheon-bu, finds a blood letter, but there are too many suspicious things to conclude as a suicide. Eventually, as a result of interrogation of Mr. Won's wife, he finds out that Mr. Won did not know the letters in his lifetime. At that time, Mr. Sa, who he had known well with Mr. Won, was murdered again with a similar technique, and Wang Seong-rim from Suncheon-bu, struggling to find a suspect, is on the verge of death...
