The case of stealing gold in Heimu city.

Tang Dynasty. A series of riches are stolen from Black Jupiter for half a year. When the riches of the ruler of Black Jupiter are stolen from him, he asks his friend's son, Red Girl, to investigate. Together with Oh Hong-soo, who accidentally saves his life, he investigates the theft, but his frustration grows as the case never seems to be solved. Meanwhile, the theft remains unsolved, and one of the victims, a scion of the Wang family, is dead. One of the victims, a scion of the Wang family, is found dead, which leads to a series of clues that finally leads Red Girl to realize that the Wang family is responsible for a series of thefts on Black Jupiter. But as she tries to keep her secret, she faces the threat of losing her life to the Wang family.