Tae-yul, Jang Hyuk, the best swordsman in Joseon who serves King Gwanghaegun as his bodyguard, refuses to join a rebellion mounted by the King’s most powerful officials who doubt his ability to lead the nation against foreign threats. One of the rebellion’s leaders, Jeong Man-sik Min Seung-ho, challenges him to a duel, and in the clash Tae-yul’s sword shatters, sending shards of metal into his eyes. The King himself intervenes, halting the duel, declaring he will abdicate the throne, and releasing Tae-yul from royal service.
Years later, an older Tae-yul lives with his teenage daughter, Tae-ok, Kim Hyeon-soo raising them as they eke out a living as mountain trappers. Tae-ok longs to glimpse life beyond their remote home, while Tae-yul insists the world is far more dangerous than she understands and fights to shield her from it. His eye injuries worsen, and a local monk warns that unless his eyes are treated with special herbs, he will go completely blind in a matter of days. The monk directs them toward the trader Hwa Seon, Lee Na-kyeong but Seon reveals the precious herbs are costly and accessible only to those with political pull.
Back in the capital, Gurutai, Joe Taslim a relative of the Qing emperor who has built his wealth by enslaving captives seized during the Qing invasion, arrives with ambitions that Joseon cannot ignore. The court frets that Gurutai might compel them to offer up their children as tribute to Qing nobles. Lee Mok-yo, Choi Jin-ho a respected court official, begins drafting a petition to resist Qing influence, and also asks Seon for help finding a young girl to care for his aging mother; Seon, in turn, recommends Tae-ok. The plan sets Tae-ok on a perilous path she does not yet fully understand.
Gurutai’s men harass Seon and her workers, and Tae-yul, armed with only a cane, steps in to defend Tae-ok. That night Tae-ok departs for Lee Mok-yo’s estate, but Gurutai and his retinue ambush the place, slaughtering Lee’s household and seizing Tae-ok as a hostage. Tae-yul survives an assassination attempt and saves Seon from a retaliatory attack by a Qing slaver, then tracks down and torches Gurutai’s main slave camp, freeing those imprisoned inside. A lone survivor guides him to Gurutai’s private compound.
Lee, leading royal guards, attempts a rescue but is overwhelmed as Qing riflemen mow down his men. Tae-yul arrives, killing the riflemen and Gurutai’s assassins before collapsing from exhaustion. He is saved by Lee and Seon, who administer the herbs. Seon admits Tae-yul will still go blind eventually, but with little time left, Tae-yul presses on. He confronts Min Seung-ho again; after a tense duel, Min yields, only to have Gurutai slit Tae-yul’s throat for losing. The two men face off in a final duel, with Gurutai’s mistress holding Tae-ok at knifepoint and a Qing envoy observing. Tae-yul gains the upper hand, but Seon’s cunning allows him to stab the mistress and then disarm and impale Gurutai, saving Tae-ok. The envoy stops his guards from intervening, allowing Tae-ok and the other slaves to escape. Tae-yul cradles his daughter as his world fades to black, slowly going blind.
A flashback reveals Tae-ok is not Tae-yul’s biological daughter but the daughter of King Gwanghaegun; the King had tasked Tae-yul with raising her to give him a reason to live. The film closes with Tae-yul and Tae-ok slowly making their way down the mountain, a man who believes he’s seen enough now ready to face the wider world with his daughter by his side.
