Deep in the ancient Joseon palace, although the crown prince Li Cang has a noble status, his road to rule is full of thorns.As the future king, he should have supreme authority. However, the reality is that the courtiers obey him in both ways, and his orders are often difficult to be truly implemented.He was just a prince in name only, his power was emptied out and his majesty was ignored.

The situation in the palace was unpredictable, and the news that the king was seriously ill was like a huge stone thrown into a calm lake, causing ripples.The crown prince Li Cang was very worried. He knew that he had a great responsibility, so he asked to enter the depths of the palace to personally take care of his seriously ill father.However, his request was rejected by the king's step-concubine Zhao.Zhao, the daughter of Zhao Hak-soo, the leader of the government, declined the crown prince's visit because she had a headache.

Faced with such a dilemma, the crown prince Li Cang did not give up.He knew that in order to truly understand his father's condition, he must find the prescription diary.Therefore, he placed his trust in his subordinate Wuying.Although Wu Ying came from a martial arts background, he has a calm personality, acts cautiously, and is a person who is loyal to the country.He silently accepted the prince's mission and began to look for traces of the prescription diary.

However, while the eldest son Li Cang was trying to find the prescription diary, a conspiracy against him was quietly brewing.Zhao Xuezhu, Zhao's father, was well aware of the ambitions and intentions of his son Li Cang.He accused the prince of pretending to be worried about his father on the surface, but in fact he wanted his father to die as soon as possible for the sake of his own power and safety.He even publicly declared that the prince was a monster-like son who was plotting rebellion, and ordered the prince's arrest.

The situation of the eldest son Li Cang is becoming more and more difficult. Not only does he have to face the betrayal and conspiracy of the courtiers, but he also has to work hard to find a prescription to treat his father.He knew that he had to be strong and not be defeated by difficulties.He believes that as long as he persists, he will one day be able to uncover the truth, restore his power, and bring light to North Korea's future.