A young maid Duk Im is ordered to visit the late Royal Noble Consort Yeong’s funeral. There she meets the Crown Prince who also secretly came to say goodbye to his grandmother. Duk Im learns about the forbidden book which King Yeongjo despises because of a certain phrase, and is warned that she’ll be losing her head if she is to read it. One day, she hears that the book is kept in the Crown Prince’s library, which makes her worried.

The tiger is on a killing spree within the palace. Unlike any other animal, it is smart. It knows exactly when to run, stop, and hunt. Although Lee San struggles with hunting this tiger, he unintentionally gets help from Duk Im as he was fooling around with her by pretending not to be the Crown Prince. To stop further casualties, this horrid tiger must be stopped.

All the young maids start to panic when they see the tiger. Duk Im comes up with a way to help the maids escape safely. San saves Duk Im, who’s in danger, but for mobilizing the military in the palace without the King’s permission, San almost receives punishment. And those who want to dethrone the Crown Prince are about to use this incident to their advantage.

Duk Im is shocked to find out San’s true identity. She gets upset as she thinks he fooled her on purpose, and therefore, she tries her best to stay away from him. However, with her outstanding skills and cleverness, she gets chosen to be his personal maid. Meanwhile, Princess Hwawan is not fond of Duk Im and finds a way to frame her and punish her.

Just as the Prince’s Lecturer orders to kill Duk Im, San appears to save her. Claiming that he was clearly mistaken, the Lecturer begs forgiveness and San lets this incident slide for now. Today is the day of the coming-of-age ceremony for the court maids. Duk Im is also very excited to celebrate this special day. However, the Queen does not make the day enjoyable for both San and Duk Im.

Lee San’s confinement still takes place. Despite the long boring time without books, Duk Im’s company helps him to stay sane. Lee San needs an ally who can closely advise the King. As Duk Im has sworn an oath to serve San, she volunteers to persuade Queen Kim. She comes up with a plan to make it possible, but whether it will actually work still remains a question.

After the incident at the bathtub, San happens to eavesdrop on the conversation of the court maids. From that conversation, he learns something that truly makes him happy. Meanwhile, something is not well with the King. Despite his great age, he maintains good health and a clear mind. However, some symptoms show that he is now not as healthy as he always used to be.

After an inspection of the court maids, a royal book that belongs to Consort Yeong has emerged from Duk Im’s belongings. Although it is a gift from the King himself, she is suspected of theft and undergoes questioning. Meanwhile, Hong Duk Ro eventually disobeys the Crown Prince and recruits a royal physician to the Dongdukhoe meeting. The reason is yet to find out.

The King suspects that San is plotting treason for bringing the soldiers to Royal Temporary Palace when he was the one who had been attacked. Now that Duk Im knows Lady Seo was forced to join Gwanghan Palace by Head Lady Cho, she tries to save her by stealing the list of signers at Head Lady Cho’s residence.

King Yeongjo orders to confine San in his chambers. Duk Im desperately wants to help San get out of the trouble and starts to think hard to come up with an idea. Duk Im happens to learn about a secret document that the promise between His Majesty and the late Crown Prince is written on. Meanwhile, San is framed for high treason and questioned by King Yeongj in front of the high officials.

The dispute over the throne finally comes to an end. Aware of his current weakness, the King admits that his current status is no longer fit to rule a country. With the help of Duk Im, the King remembers the promise he has with his late son. A promise that he will make San the next king of Joseon. Now, a new sky has risen, and San prepares to become what he has been trained for his whole life.

Not everyone is happy with San becoming King. Late night, an attack is made on San’s life. Although San survives thanks to his Royal guard, he finds out that his stepbrother is a part of the treason. Regardless of the rebel, San is in deep grief of having to kill a family member. Meanwhile, Duk Im seems to be constantly drifting away from San due to various events. Their love just seems impossible in any way.

Wonbin suddenly falls into critical condition. Although she has absolutely no problems with her health, she suddenly meets her death at a young age. Despite Duk Ro’s great grief for losing his younger sister, he still must fulfill his task in finding the court maids who suddenly went missing. As Kyung Hee is also one of the missing maids, Duk Im sets out on her own to find her close friend.

San orders Duk Im to leave the palace. After one year, Duk Ro and Duk Im run into each other at the street market, and Duk Ro suggests to her that she should run away with him. Meanwhile, San happens to stay the night at Princess Cheongyeon’s place and sees Duk Im after a long time. However, San decides to put the past behind and selects a new royal concubine.

Consort Hwa is infuriated with jealousy, and she tries to sabotage Duk Im with the help of Queen Dowager. Consort Hwa frames Duk Im for having relations with a man and makes Queen Dowager interrogate her. Therefore, all four of them, including San, gather at Consort Hwa’s chambers, and San makes his final decision.

The Crown Prince did not manage to survive the sickness. Although Duk Im and San fall into great grief, they regain their strength quickly for the sake of the country and their unborn baby. However, due to the plague and other events, close people around them pass away. Despite the numerous incidents, San remembers his duty as king and stands firmly to put the country on the path to peace.