Set in 1506 during the final months of King Yeonsan's tyrannical reign over the Joseon dynasty in Korea, the novel follows seventeen-year-old Iseul and Prince Daehyun as their separate struggles against the crown converge into a conspiracy to overthrow the kingdom's worst tyrant.
Iseul, the younger daughter of a magistrate executed two years earlier during one of the king's political purges, has been living in hiding with her older sister, Suyeon. When a quarrel drives Iseul outside and Suyeon follows, the king spots the elder sister and kidnaps her. Yeonsan routinely abducts women across the kingdom, holding over a thousand captives. Iseul treks three days through the king's forbidden territory, a vast hunting ground carved from Gyeonggi Province by evicting tens of thousands, determined to rescue Suyeon.
Near the capital, Iseul finds shelter at the Red Lantern Inn, run by Madam Yul, a sharp nineteen-year-old innkeeper. She meets Wonsik, a former investigator for the
Uigeumbu (the State Tribunal), who warns that stealing a woman from the king means death. Iseul learns of a killer called Nameless Flower who murders officials loyal to the king and leaves taunting bloody messages. She conceives a desperate plan: Find the killer and offer Nameless Flower to the king in exchange for Suyeon.
The narrative alternates with Prince Daehyun, the king's illegitimate half-brother. A shaman prophesied at his birth that he would die this year, and Daehyun is resolved to survive long enough to commit treason. Two years earlier, Yeonsan orchestrated a horrific incident in which Daehyun's foster brothers were tricked into beating their own mother to death, leaving Daehyun emotionally numb. With his closest friend, Royal Guard Min Hyukjin, and aided by Wonsik and Yul, Daehyun plots a coup but lacks the political influence to lead one.
Iseul investigates Nameless Flower under Wonsik's reluctant mentorship, pocketing a red wax bead from a crime scene. Wonsik gives her the
Muwonrok, a treatise on forensic medicine, and insists she deduce the bead's significance herself. After an encounter in the forest where Daehyun accidentally shoots her with an arrow, grazing her shoulder, Iseul vows revenge. With help from Yeongho, a court jester who frequents the inn, she infiltrates the Royal Academy disguised as a servant and locates Suyeon among captive women. Her sister bears a bruise on her throat and insists Iseul leave. As Suyeon is escorted away, a repulsive official Iseul calls "Maggot" (Official Wu Sayong) gropes her.
A turning point arrives when Daehyun discovers Lady Seungpyeong, the king's fifty-year-old aunt-in-law, killed herself after being raped and impregnated by Yeonsan. Her brother is Deputy Commander Park Won Jong, the king's most powerful military aide, and revealing the truth could transform him from loyal servant into furious enemy.
Nameless Flower lures Hyukjin to Mount Acha with a forged letter. Daehyun finds his friend hanging from a tree, still alive, but the killer attacks, shoves Hyukjin off a cliff, and knocks Daehyun unconscious. Iseul discovers Daehyun wounded nearby; he promises to help her reunite with Suyeon if she helps him escape. During their journey, he reveals his plan for a coup and argues that only overthrowing Yeonsan will free Suyeon. Iseul reluctantly agrees to pursue both paths: finding the killer and joining the rebellion.
Iseul's investigative skills sharpen. She deduces that the wax bead matches hat strings worn by royal guards, and a witness's dying description of "half man, half wolf" refers to the feathered military hat. Nameless Flower is a royal guard or someone disguised as one. Through her uncle, Government Official Choi Ikjun, Daehyun gains access to Deputy Commander Park, who agrees to spearhead the rebellion after learning how his sister died. A dozen senior officials join, planning to depose Yeonsan and install Grand Prince Jinseong on the throne.
At the conspirators' gathering, Maggot reveals a devastating truth: Iseul's uncle betrayed her parents to the king years earlier, trading their secret for a promised promotion. Uncle Choi later reveals that the coup leaders plan to distribute the king's captive women as rewards, with Suyeon going to Maggot as his concubine. When Daehyun fails to reverse this decision, Iseul resolves to enter Wongaksa Temple disguised as a courtesan to protect her sister from within.
Wonsik is killed defending Iseul and Daehyun from
chehongsa officers (the king's designated kidnappers), sacrificing himself so they can escape. His death shatters Iseul, and Daehyun's cold detachment provokes a painful rift before they reconcile, their growing feelings for each other increasingly difficult to deny.
On the eve of the coup, Nameless Flower kills Iseul's uncle and threatens to personally kill the king. Yeonsan cancels his trip to Kaesong City, which would have drawn thousands of soldiers from the capital, and remains behind, nearly derailing the rebels' plan. Inside the palace, Iseul finds Suyeon broken and suicidal. She traces the word
banjeong, meaning "righteous rebellion," on her sister's palm, coaxing a flicker of hope.
The rebellion launches that night. Most royal guards abandon their posts or join the uprising. Iseul rallies dozens of captive women, warning them the coup leaders intend to keep them as spoils, and leads them toward a mountain gate. Daehyun arrives with freed prisoners and helps hoist the women over the palace wall. In a wrenching farewell, he tells Iseul that if they do not meet in this lifetime, he will find her in the next.
Escaping through the mountains, Iseul pieces together Nameless Flower's identity. Royal Guard Gunwu, Wonsik's estranged son, reveals he hid a gold pouch at Hyukjin's murder scene, identifying its contents as salt. Iseul connects the pouch to a similar one carried by Yeongho, filled with limestone powder used in burial rituals; the flowers left at murder scenes grow from limestone sprinkled on graves. Yeongho is Nam Seungmin, the son from a cold case Wonsik once investigated, whose mother was killed and buried in her own garden. As a boy, Seungmin mocked King Yeonsan for weeping over his executed mother's bloody robe, and the first Nameless Flower murder bore a similar taunt.
Iseul races to warn Daehyun, finding him on a cliff tracking the deposed king, teetering on the edge of vengeful violence. Yeongho emerges, confesses his desire for glory as a king-killer, and shoots Daehyun with an arrow. In the struggle, Iseul stabs Yeongho, and Daehyun locks his arm around the killer's throat. Both men tumble off the cliff into the river. Iseul believes Daehyun is dead.
Months of grief follow. Suyeon recovers at the Red Lantern Inn, where Yul and the freed women build a community. The new government disappoints: Coup leaders hoard land and tax exemptions, and captive women are distributed as rewards. Over a year later, Gunwu delivers Iseul's mother's double ring, which she had given Daehyun as a talisman, and confesses that Daehyun survived because Wonsik's journal absorbed the arrow's impact. Daehyun has been living as a fugitive after secretly assassinating Maggot to protect Suyeon and is departing for exile on Jeju Island in thirteen days.
Iseul rides to the southern port of Mokpo. The next morning she encounters Daehyun; he stayed an extra day, unable to leave without one last glimpse of her. She forgives his year-long deception, recognizing his choices secured her sister's safety, and decides to accompany him to Jeju. He asks her to call him by his birth name, Yi Kyung. An epilogue set eight years later follows Kyung and Iseul as they return to the mainland to visit Wonsik's grave and reunite with Suyeon at the Red Lantern Inn. Kyung reflects that the death prophecy from his birth was not the story of how his life would end, but of how it would begin.