Lee Yool falls off a cliff and nearly dies in an attempted assassination. He loses his memory, and wanders for 100 days under a new name and personality. During this period, he meets Hong Sim, head of the first detective agency in Joseon.
Episode 1
Lee Yul begins a secret investigation after growing suspicious of his worsening health. Yeon Hong-sim returns to Hanyang in search of her brother.
Episode 2
Yul uncovers the mastermind's identity and Kim So-hye's secret before coming under attack in the forest. Hong-sim is punished for refusing to wed.
Episode 3
Yul loses all memory, but gains a new identity as Na Won-deuk. Hong-sim begrudgingly chooses to become a wife to avoid life as a concubine.
Episode 4
Jung Je-yun searches for a link between the royal physician's murder and Yul's disappearance. Hong-sim puts Won-deuk to work to repay his debt.
Episode 5
News of the crown prince's passing is made public. Hong-sim is delighted to learn of Won-deuk's ability to read and write.
Episode 6
Hong-sim's reunion with her brother doesn't go as expected. Eunuch Yang notices something off about the crown prince's dead body.
Episode 7
Witnessing Won-deuk's martial arts skills, Hong-sim gets curious about his real identity. News of the queen's talisman sparks protest and debate.
Episode 8
Won-deuk celebrates an unforgettable birthday. Mu-yeon completes his final task for Kim Cha-eon and prepares to leave with Hong-sim.
Episode 9
Je-yun reunites with Hong-sim as the new county governor. To recover his memory, Won-deuk visits Hanyang and enters palace walls.
Episode 10
With Hong-sim and Won-deuk's help, Je-yun concocts a plan to get in Park Seon-do's good graces. Rumors swirl about the crown prince being alive.
Episode 11
The king tries to regain control of his throne. Hong-sim and Won-deuk settle their affairs prior to leaving. Je-yun sees Yul in Won-deok.
Episode 12
Cha-eon interrupts the coronation ceremony with a shocking announcement. Yul has trouble moving on from his memories with Hong-sim.
Episode 13
Hong-sim searches for Mu-yeon in Hanyang with her father and Je-yun in tow. Yul's competency is tested by a visiting envoy.
Episode 14
Won-deuk and Hong-sim reconnect as Yul and Yoon I-seo. Je-yun assists Yul in his quest to find his diary — and answers.
Episode 15
Having regained his memory, Yul seeks revenge on a killer in his midst. Cha-eon plans bloodshed to achieve his goals.
Episode 16
Cha-eon leaves behind his final wish. Moved by the king's hopes and Je-yun's plan, Yul makes good on his promise to I-seo.
