In 180 B.C., after enjoying its golden age for 2100 years, the Gochosun Kingdom finally falls as the result of a year-long war with the Han Empire. The Emperor of the Han Dynasty divides the territory that previously belonged to Gochosun into four different administrative districts (Nak Rang, Jin Beon, Im Doon and Hyeon To) and deploys his military. People of Gochosun strongly stand against the Han Dynasty. Hae Mo Soo is the central figure of the resistance.
The king of Bu Yeo, Hae Bu Roo, is very pleased with the fact that people of Gochosun are settled in Bu Yeo with the help of Hae Mo Soo. However, he’s deeply concerned when Bu Deuk Bool tells him that protecting people of Gochosun might invite the Emperor’s anger.
Meanwhile, Yeo Mi Eul, oracle of Bu Yeo, sees a three-legged crow appear in the Sun. She knows that the two legs represent Hae Bu Roo and Geum Wa, but she isn’t sure who the other person is.
The governor-general of Hyeon To calls a meeting for all the tribal chiefs. Geum Wa goes to the meeting in place of his father. There, he meets Yu Hwa. The governor-general warns that whoever harbors Hae Mo Soo will be severely punished. He kills innocent Gochosun refugees in front of the tribal chiefs. Geum Wa gets enraged, but for the fear of future troubles, he can’t do anything. All of a sudden, Yu Hwa comes in and calls out to the governor-general to stop.
Accused of harboring Hae Mo Soo, everyone in Yu Hwa’s tribe members gets killed except her. However, Hae Mo Soo manages to sneak away. He happens to meet Yeon Ta Bal and his group. He’s shocked to hear that the whole tribe was murdered because of him. Yeon Ta Bal Soon realizes that the man who seems very shocked about the news is Hae Mo Soo. In order to turn him in, he hires Hae Mo Soo as his help. Later, someone attacks Yeon Ta Bal and his group, but Hae Mo Soo helps them escape danger. That night, Geum Wa rescues Yu Hwa and runs away with her. She tells him that Hae Mo Soo is still alive.
Meanwhile, Yeon Ta Bal’s wife gives birth to a baby girl. Yeon Ta Bal names her So Seo No. He pledges that he’ll raise his daughter stronger and wiser than any other man in the world.
Geum-wa hears from Bu Deuk Bool that his father lured Hae Mo Soo into a trap. He is devastated. He plans to help Hae Mo Soo escape. With the help of Geum-wa and his soldiers, Hae Mo Soo manages to escape. However, he’s struck by an arrow and falls from a cliff.
Yoo Hwa gives birth to a boy. She names the boy ‘Ju Mong’. She tries to leave Bu Yeo with her baby. However, Geum-wa insists that she stay and raise Ju Mong in Bu Yeo. In order to protect the baby, whose father is Hae Mo Soo, Geum-wa decides to raise him as his own son.
Meanwhile, Yeo Mi Eul has a vision that the three-legged crow in the Sun flew away. She believes that it’s an ominous sign. She tells Bu Deuk Bool about the omen. He suddenly realizes that Yoo Hwa’s baby might be the son of Hae Mo Soo. He orders Jeok Chi to kill the baby. Yoo Hwa becomes aware of the danger and flees with the baby. Soon, she’s caught by the Han soldiers. Jeok Chi shows up and gets rid of the Han soldiers. However, he tells Yoo Hwa that it was Hae Bu Roo the king of Bu Yeo who wanted Hae Mo Soo dead. He’s about to kill Yoo Hwa and Ju Mong with a sword raised overhead.
Twenty years later…
King Geum-wa’s continuous conquest almost doubles Bu Yeo’s territory.
King Geum-wa realizes that Ju Mong didn’t attend Young Go Je (a ritual when people celebrate the harvest and thank God). He finds out that Ju Mong is locked in a barn for harassing Bu Young. He’s very disappointed with Ju Mong. He orders that Ju Mong receive twenty lashes. However, Dae So asks the king reduce the punishment, saying that the following day Ju Mong and he are supposed to go looking for Dae Mool Hwal (a legendary bow that the founder of Bu Yeo always carried with him). Geum-wa grants Dae Soh’s request.
Ju Mong promises himself that he won’t do anything inappropriate. He also promises that he’ll never disappoint his mother. Dae Soh, Young Po and Ju Mong leave the palace to look for Dae Mool Hwal. Ju Mong takes the lead. While passing the foggy mountain paths, Ju Mong gets separated from his friends and gets lost. He tries to look for his friends, but he gets stuck in a swamp. So Seo No and her group pass by and help Ju Mong. Ju Mong is surprised that the leader of the group is a woman. He’s very impressed by her leadership and beauty.
Meanwhile, Dae Soh and Young Po arrive at the Founder’s Mountain. They find an old poem on the map indicating the location of Dae Mool Hwal. However, they can’t figure out the meaning of the poem. After dark, they manage to understand the meaning and rush to the cave where Dae Mool Hwal is located.
Dae Soh is surprised to see Ju Mong alive. He orders Young Po to keep an eye on Ju Mong’s every move. Yoo Hwa tells Ju Mong that he should become the king of Bu Yeo and accomplish a very important task. She introduces Moo Song, a master of martial arts to Ju Mong. Seeing Ju Mong’s baby-like soft hands, Moo Song tells Ju Mong to climb up and down the mountains. Ju Mong gets impatient and annoyed because Moo Song only makes him climb the mountains instead of teaching him real martial arts. One day when he confronts his master, Moo Song takes him to a prison cell located inside a dark cave.
Ju Mong finally starts learning the basic moves of the martial arts. His skills are improving every day.
King Geum-wa hears that they successfully made a new weapon from iron. Excited by the news, Bo Deuk Bool and the king go to see the new weapon. When they’re about to test the new weapon, Dae Soh volunteers. He suggests that Ju Mong and he fight with the new swords. Hesitant at first, Ju Mong agrees to fight with him.
Meanwhile, So Seo No and the group of merchants come back to Jol Bon from Ok Jeo. Yeon Ta Bal is very happy about his daughter’s successful deal. He tells So Seo No, Gye Pil and Woo Tae that he will make every effort to obtain Boo Yeo’s secret method of iron weapon manufacturing. He emphasizes that it’ll be the only way for Jol Bon to survive among other surrounding countries.
Bu Deuk Bool hears that Hae Mo Soo is still alive. Yeo Mi Eul and he go see Hae Moo Soo who is locked in a prison. When Moo Song brings them to the prison, Ju Mong hides himself and overhears their conversation. After confirming that Hae Mo Soo is alive, Bu Deuk Bool asks Moo Song not to tell anyone that he came.
Dae Soh finds out that Ju Mong secretly leaves the palace every night. He takes Ju Mong to the training field and gives him a sword. He volunteers to teach Ju Mong how to become a good swordsman. Ju Mong is surprised, but he accepts Dae Soh’s proposal.
In the middle of the night, Ju Mong visits Mo Pal Mo at the weapon manufacturing yard. Ju Mong asks Mo Pal Mo to make him a sword as strong as Dae Soh’s. Mo Pal Mo doesn’t know what to do because he knows he needs the king’s permission to do so.
Meanwhile, the Xianbei (nomadic people residing in modern Manchuria and eastern Mongolia), who acquired the steel weapons, keep invading Hyeon To. King Geum-wa hears that the newly appointed general-governor of Hyeon To will visit Bu Yeo. He has a bad feeling about his visit and calls up all the statesmen.
Yang Jeong, new general-governor of Hyeon To, sends King Geum Wa a letter. In the letter, he informs the king that he’ll regularly check on Bu Yeo’s weapon manufacturing facility to make sure that it remains closed. Insulted by Yang Jeong’s arrogance, King Geum Wa orders to burn the letter. Beol Gae suggests that the king proclaim the Prince Royal to the throne as soon as possible, in order to strengthen the royal authority. However, King Geum Wa tells him that this isn’t the right time yet. He orders not to bring up the same subject again. Won Hoo hears that the king delayed Ju Mong’s investiture. He believes that King Geum Wa is hesitant because Ju Mong isn’t qualified to become the king. Young Po decides to get rid of Ju Mong. He sends an assassin. Ju Mong is stabbed by the assassin in the street. Ma Ri, Hyeop Bo and O Yi happen to find Ju Mong who is injured and unconscious. They take him to Bu Young.
Meanwhile, Yeon Ta Bal plans to raid the smuggler, Do Chi, in order to seize control of the salt market. However, while making a surprise attack on Do Chi, So Seo No is kidnapped by Do Chi.
Ju Mong finds out that So Seo No is captured by Do Chi. He helps So Seo No escape. At first, So Seo No didn’t trust Ju Mong, but she soon realizes that he’s trying to help her. Yeon Ta Bal and his soldiers come to rescue So Seo No, as well.
O Yi, Ma Ri and Hyeo Bo find out that Ju Mong released So Seo No. They try to kill him. To save Ju Mong’s life, Bu Young can’t help but tell everyone that Ju Mong is the Prince of Bu Yeo.
King Geum Wa gives Dae So and Young Po access to the weapon manufacturing facility. He orders them to find out the secret method of iron weapon manufacturing.
While looking for a place to hide, Ju Mong remembers the prison inside the cave. Searching for Ju Mong, Lady Yoo Hwa and Moo Deok finally find him in the cave.
Carried away by Hae Mo Soo’s splendid demonstration of swordsmanship, Ju Mong begs Hae Mo Soo to teach his swordsmanship to him. Hae Mo Soo, getting Ju Mong seated near, sweeps Ju Mong from head to waist. With his hand on Ju Mong’s back, Hae Mo Soo asks him to stop breathing. The moment Hae Mo Soo takes his hand off Ju Mong’s back, Ju Mong gets his breath back but falls on the ground unconscious. Dae So and Young Po, with their soldiers, head for the cave prison to murder Ju Mong when King Geum Wa, at the same time, under escort leaves for the prison to see it for himself. Into the prison where Hae Mo Soo and Ju Mong are in training move Dae So and Young Po launching harsh attacks. Ju Mong’s tensed look becomes dismayed when the disguised assassins, including Young Po, reveal themselves. In the meantime, King Geum Wa’s guards, who arrived at the cave prison later, report to the king on the site of the scattered corpses and he furiously gives an order to investigate the case thoroughly.
King Geum Wa after hearing the news that Hae Mo Soo is still alive looks up in the air and falls into a deep thought. Lady Yoo Hwa visits king Geum Wa and breaks into tears thinking of Hae Mo Soo, when the king starts to drink and talk about him. Gye Pil approaches Mo Pal Mo, who was drinking alone, and treats him to free drinks. While Mo Pal Mo strolls outside the Bu Yeo Palace, Ju Mong appears and asks if any swords are available.
Hae Mo Soo takes out a bamboo letter, hands it over to Ju Mong and tells him to deliver it to King Geum Wa without revealing his status. Ju Mong calls for Moo Deuk’s help to deliver the bamboo letter, and King Geum Wa, while reading wooden letters from Yeon Ta Bal, finds the bamboo letter and gets nervous.
Ju Mong visits So Seo No and asks her to take O Yi, Ma Ri, and Hyeo Bo in Yeon Ta Bal’s commerce band, but So Seo No refuses. Dae So and Na Ro visit the commerce band to Ju Mong’s surprise, but Ju Mong greets them with courtesy. While Ju Mong, Dae So and So Seo No together have a tea break at Yeon Ta Bal’s office, Dae So treats Ju Mong as if nothing has happened between them. After asking So Seo No to excuse himself for a while, Ju Mong approaches Dae So, kneels down before him and begs for his life. Dae So, infuriated by the past 20 years of miserable memories of Won Hoo and himself, promises not to forgive the insolence again. King Geum Wa calls General Heuk Chi and an orders him to find Hae Mo Soo, the runaway from the cave prison. Bu Deuk Bool, from a distance, watches with a worried look.
Meanwhile, Hae Mo Soo suddenly pulls out his sword toward an approaching object.
Hae Mo Soo reunites with Yu Hwa as arranged by Yeo Mi Eul. Yu Hwa tells him everything she had kept buried deep in her heart during the years past as tears keep flowing from her eyes. After an emotionally charged meeting with Yu Hwa, Hae Mo Soo returns to his mountain hideout to find Ju Mong soundly asleep. As he quietly lays his hand on Ju Mong’s cheek, tears fall from his face.
Back at the Palace, Yu Hwa confesses to Geum Wa that she has met Hae Mo Soo. Utterly shocked, Geum Wa tells her that he, too, has been desperately looking for Hae Mo Soo and asks her to tell him Hae Mo Soo’s whereabouts…
Ju Mong learns archery from Hae Mo Soo in the grasslands near his mountain hideout. Saying a master archer must be a fast shooter, Hae Mo Soo astonishes Ju Mong by firing a second arrow even before the first arrow reaches the target. Determined to leave Buyeo, Hae Mo Soo sends off Ju Mong telling him to go visit his mother.
Meanwhile, Dae Soh approaches Hae Mo Soo’s hideout on the mountain leading some two hundred soldiers as Geum Wa and Yu Hwa in disguise leave the Royal Palace secretly, under the protection of armed guards.
Ju Mong hurries back to the Palace at the news of his mother’s critical condition. Tears well up in his eyes the moment he sees Yu Hwa’s thin and haggard figure... Meanwhile, Dae So and Won Hu are struck speechless when they hear from Young Po that Geum Wa personally brought Ju Mong back to the Palace from outside, but they struggle to get their poise back.
Mo Pal Mo says he has something very important to tell Ju Mong and takes him to his quarters, where he says Young Po and the palace messenger are smuggling weapons out of the iron workshop. Stunned by the news, Ju Mong mulls over for a moment and suggests that they had better pretend that they know nothing about it as divulging the fact would endanger their lives.
King Geum Wa calls Ju Mong to his quarters. He asks Ju Mong for the identity of the assassin who tried to kill Ju Mong, but Ju Mong answers he doesn’t know…A moment later, Geum Wa inquires Ju Mong about his exceptional martial arts skills, and Ju Mong answers that he acquired them from a teacher named Hae Mo Soo while he was living outside the Palace.
Meanwhile, King Geum Wa calls up all the statesmen, Won Hu, Yu Hwa, Ju Mong, Dae Soh and Young Po to his quarters, and drops a bomb that he convened the meeting because he wanted to discuss what they should do about proclaiming the Crown Prince.
Ju Mong leaves the Palace and goes to Yeon Ta Bal, and asks him to hire him. Yeon Ta Bal, in response, says he needs some time to think it over, and collect the opinions of So Seo No, and Woo Tae. Oh Ma Hyeop, who thought Ju Mong’s return to the Palace would give him an opportunity to get a good position in the Palace, is disappointed by Ju Mong’s sudden announcement…
Upon hearing that Ju Mong is working for Yeon Ta Bal, King Geum Wa relays the news to Yu Hwa who becomes worried about Ju Mong, not knowing what her son’s motive is.
Dae Soh and Bu Deuk Bul go to Hyeon To’s Palace to settle the salt trade matter on behalf of King Geum Wa. Yang Jeong says that he has nothing to say to the two and that the only way to resolve the issue is for King Geum Wa to come to him and receive the order of Han’s Emperor…To this, Bu Deuk Bul suggests to Dae Soh that they should return to Buyeo and seek other options rather than endure such insult, but Dae Soh is determined to resolve the case before returning.
Meanwhile, Yeo Mi Eul visits Geum Wa after much deliberation and expresses her resentment at Geum Wa’s sole decision on how to install the Crown Prince. Geum Wa says he can’t discuss state affairs of Buyeo with Yeo Mi Eul, for she is responsible for Hae Mo Soo’s incarceration for twenty years and his death.
Yeo Mi Eul summons the priestesses from Buyeo’s all four regional districts and says that King Geum Wa is trampling on the authority of the oracle, stressing that they must stop him. Hyeon Mu, one of the priestesses listening to Yeo Mi Eul, relays the unbelievable news that she has seen the Da Mul Bow (a legendary bow that the founder of Buyeo always carried with him) broken in the cave in the Mountains.
Yeon Ta Bal has been watching Ju Mong practicing with his bow and says he has never seen a better archer than Ju Mong in his whole life. Remembering Hae Mo Soo who once saved him from trouble with his superb martial arts skills, Yeon Ta Bal is quite surprised to find out Ju Mong was trained by none other than Hae Mo Soo himself.
Meanwhile, So Seo Noh, upon hearing the news that Dae Soh has returned after settling the conflict with the Han Empire, visits him in his quarters. Delighted by her visit, Dae Soh brings out a wooden box on to the table. Precious stones are inside the box.
So Seo Noh pleads to her father Yeon Ta Bal to let her and Ju Mong lead the merchants to the nation of Go San, and Yeon Ta Bal decides to see what his daughter is capable of. Ju Mong, So Seo Noh, Oh Ma Hyeop and Sa Yong make their preparations for the journey to Go San. Ju Mong visits his mother in her quarters and tells her that he is going to Go San for the salt trade. After thinking for a moment, Yu Hwa takes off the jade ring that she wore around her neck and hands it to Ju Mong, telling him to give it to the woman he loves. Yeo Mi Eul sits at the same table with So Ryeong, the youngest priestess in Bu Yeo, who says that she’s been pressed under a mysterious power ever since she entered the Palace and Yeo Mi Eul remembers how Byeo Ri Ha fainted in front of Ju Mong.
Ju Mong and So Seo No fight off masked men who raided the group. So Seo Noh gets mixed feelings after discovering that one of the fallen men was a military official whom she often encountered while trading weapons with the nation of Haeng In. While Hyeop Bo and Ma Ri insist on continuing the journey, Ju Mong says he will follow So Seo No’s decision since she is the leader.
Geum Wa is troubled by the Han Empire’s request to dispatch Bu Yeo’s 10,000 soldiers for its battle against the southwestern barbarians. To prevent his achievement from being wasted in vain, Dae Soh proposes negotiations to Yang Jeong, saying that Bu Yeo will send its troops conditionally, but Geum Wa decides to prepare a war with the Han Empire.
So Seo Noh is determined to abort the journey but decides to wait on account of Ju Mong who asks her to give him two days of time. To carry on the journey, Ju Mong sneaks into the mountain hold of the bandits, but ends up getting caught, and So Seo Noh enters the hold to make a deal with the bandit leader.
Risking her own life, So Seo Noh jumps into the enemy hideout to rescue Ju Mong and proposes a deal to Bae Mang. Ju Mong and Oh Ma Hyeop, both locked in a cell, are dumbfounded to see So Seo Noh so unexpectedly.
Upon hearing from Do Chi that Ju Mong and other members of the merchant group will be soon killed by Bae Mang, Young Po runs to Won Hoo’s quarters and relays the news with a huge smile on his face. However, Dae Soh scolds Young Po for blabbing about things he has only heard at second-hand.
Bu Young meets with Yu Hwa, and tells her that Ju Mong is in grave danger. Driven by misgivings, Yu Hwa decides to report the situation to Yeon Ta Bal.
Meanwhile, as people crowd each and every street of Bu Yeo to get salt, and fights amongst them ensue, Geum Wa feels increasingly troubled…
Ju Mong and So Seo Noh stand before King Geum Wa. Ju Mong proudly says that Bu Yeo does not need to go to war with Ok Jeo now that he has found a salt mountain that will ensure a sufficient salt supply for generations to come. Highly delighted by Ju Mong’s announcement, Geum Wa says he will hold a banquet to celebrate. Dae Soh and Young Po watch them with a devastated look on their faces.
So Seo Noh says she should go back to the merchant group but Ju Mong suggests that she pay a short visit to his mother with him. The two and Yu Hwa talk over tea at Yu Hwa’s residence. Ju Mong says that So Seo Noh saved his life by striking a deal with the bandits and it was also So Seo Noh who helped him get out of a swamp long ago. Quite impressed, Yu Hwa smiles warmly as she looks at So Seo Noh.
Dae Soh is troubled to hear from Oh Yi that Ju Mong is trying to figure out the secret of making stronger iron. Young Po goes to Do Chi to thank him for saving his face.
Ju Mong, back at the Bu Yeo Palace from Hyeon To where he was dispatched as King Geum Wa’s special envoy, says he has delivered Geum Wa’s message to Yang Jeong that the Han Empire has frequently intervened with Bu Yeo’s affairs and Bu Yeo will be prepared to go to war if it continues to meddle with Bu Yeo’s business. While all statesmen are stunned at Ju Mong’s announcement, King Geum Wa laughs heartily and praises Ju Mong.
Dae Soh calls in the blacksmith’s assistant director Dok Gu to ask him on the progress of the iron weapon manufacturing. Trembling with fear, Dok Gu confesses that not long ago, he accidentally made a sword that could easily stand comparison with the strong iron swords of the Han Empire…