Yun Won-hyeong meets his sister, the queen, who asks about a girl's whereabouts; he assures her that the child is dead; when Ga-bi dies in childbirth, the prison official Cheon-deuk finds himself in charge of the motherless girl; he names her Ok-nyo.

Yun Won-hyeong has her fortune read by Ok-nyo and learns about her past; an inmate of Jeonokseo Prison asks Ok-nyo to deliver a letter for him but trouble awaits outside the prison walls.

Ok-nyeo finds a hidden cell beneath Jeonokseo Prison; inside is Park Tae-soo, imprisoned for 20 years; he initially wants to die, but soon discovers a reason to live.

Ok-nyeo seeks answers about her mother's death, showing rings to Park Tae-soo; she gains a clue and decides to become a police inspector to uncover more information.

Ok-nyeo accepts a secret spy position against her mentor's wishes; her final training stage is a dangerous real-world field assignment, testing her skills and resolve.

Ok-nyeo passes her spy test and gets her first mission; she encounters Yoon Tae-won, whom she knew from Jeonokseo Prison.