Set in the Joseon Dynasty, the film takes viewers on a gripping journey through the chaos of war and the aftermath of a pair of childhood friends who have turned against each other. Cheon-yeong is a skilled slave who struggles to escape the injustice of being a slave, while Jong-ryeo is Cheon-yeong's master, a member of one of Joseon's most influential military families. Kang Dong-won plays Cheon-yeong, a civilian with superb swordsmanship who desperately tries to change his fate as a slave. Park Jung-min plays Jong-ryeo, a descendant of Joseon's most famous military family, who takes Cheon-yeong in and later joins the imperial army, becoming the right-hand man of the reigning King Seonjo. Cha Seung-won plays the king Seonjo, who abandons his people to protect himself, Kim Shin-rok plays Beom-dong, Jin Sun-kyu plays Kim Ja-ryeong, a general of noble birth who leads the People's Volunteer Army, and Jung Seong-il plays Kenshin, a brutal Japanese pioneer.