A series of deaths of prominent politicians leads to a nighttime battle in which one member, a female, of what is apparently an assassin duo, is captured.

Shortly after the Japanese invasions of Korea in the middle of the Joseon period, a military unit of elite soldiers (made up of students of the Clear Wind Shining Moon sword school) is created to ensure the peace and the security/safety of the country.

But a political coup d'etat plot (it is referred to as a "rebellion" in the film) forces Gyu-yup, threatened with the death of his entire unit of elite soldiers, to not only kill his fencing master, but also Ji-hwan, who is seeing the female assassin from the night battle, Shi-young (who was also a warrior at the time, and the daughter of the school's fencing master).

The current king (the usurper general who, in Gyu-yup's flashback, is the commander who forces him to choose between the deaths of his men and leading his men against Ji-hwan, Shi-young, and the training master) himself becomes embroiled in what amount to attempts to cover up his tracks and betrays at least one of his foremost commanders by ordering his assassination.

The movie ends by freezing the old friends, united in battle again, in action against the usurper king's troops.