The palace is in confusion with the announcement that Jang Ok Jeong will become a concubine. Western factions are concerned that it will give Namin more power. Then, Jang Ok Jeong becomes pregnant. One year later, Jang Ok Jeong has been promoted to the highest ranking concubine and Southern Faction wants her son to be named Crown Prince. But, Queen Dowager disagrees with the idea. Suddenly, Queen Dowager is seriously ill. Cheon Soo says that if her tonics are mixed with unprescribed herbs, there can be a toxic reaction. Then Dong Yi remembers that she found an unprescribed herb in Jang Ok Jeong's ladies' quarters.

Jang Ok Jeong and her family will be in trouble if they are found guilty of poisoning the Queen Dowager. She then realizes that it is an opportunity to frame the Queen and takes her title. But, both of them are suspects and because the King doesn't know who to believe, he orders Chief Seo to investigate. Jang Ok Jeong's brother wants to kill Dong Yi, in which she refuses at first. But then, when she sees Dong Yi is talking with the King, she accepts her brother's proposal. Then, police finds all the evidence that connect the official who poisons the Queen Dowager to the Queen. Although it is all a set up, the Queen's family and court ladies are arrested and questioned. Meanwhile, Dong Yi and Cheon Soo go out to investigate the matter more thoroughly.