Hong Ra On (Kim Yoo Jung) is a young woman during the Joseon Dynasty who makes a living by dressing up like a man and giving relationship advice to the lovelorn young men who seek her counsel. A love letter that Ra On writes for a client brings her in contact with Lee Yeong, who is the Crown Prince Hyo Myeong (Park Bo Gum), the first son of King Sunjo (Kim Seung Soo) and heir to the throne. But neither knows the true identity of the other. As Lee Yeong becomes strangely drawn to Ra On, the crown prince’s eunuchs brings her into the palace as one of their own, giving her insights into palace life that no woman has seen before. Inside the palace, Ra On becomes entangled with the poet Kim Sat Gat (Kwak Dong Yeon), Lee Yeong’s trusted confidante; scholar Kim Yoon Sung (Jinyoung), who is the crown prince’s nemesis; and Jo Ha Yeon (Chae Soo Bin), the chosen royal consort for Lee Yeong. Can Ra On survive the royal palace life without being exposed as a woman?.