It is the winter of 1505. Gil Dong is born to Ah Mo Gae and his wife, who are both servants living in their master’s house. Since he was born, Gil Dong has shown unusual, physical strength. There has been a legend about the Mighty Child who, if born, will be killed by the King.

The fish sell well and Ah Mo Gae comes home with money. He decides to become a free man along with his entire family and secretly gathers money so that he can pay for their freedom. He continuously reminds Gil Dong to control his anger and to hide his strength from others. Meanwhile, Ah Mo Gae’s wife tells him that she is pregnant.

Gil Dong spots his father coming out of Lord Jo’s house covered in blood. Lord Jo’s wife tells the district magistrate that it must’ve been Ah Mo Gae who murdered her husband since he has a grudge against him. Ah Mo Gae is beaten and imprisoned. Meanwhile, Lord Jo’s uncle tells the district magistrate that it was actually Gil Dong who attacked him.

After being threatened by Ah Mo Gae, Lord Jo’s wife tells the magistrate that it wasn’t Ah Mo Gae who killed Lord Jo. After being set free and no longer a slave, he moves to Ikhwa-ri with his children. There, he and his entourage start selling goods, and he gradually gains power.

Many years have passed and Gil Dong is now a young man. Unlike the past, he has lost his mighty strength and travels on foot, selling women’s merchandise. His father, Ah Mo Gae, has become the most powerful man in Ikhwa-ri. Meanwhile, Gil Dong meets Gong Hwa and Ga Ryung. The former tells him that she’d like the King to become her lover.

Ah Mo Gae’s men find Yeo Mi, Prince Choong Won’s runaway servant. They cut her hair and lie that she has died. Ah Mo Gae’s children and men struggle to get him out of prison. He asks Heo Tae Hak to let him see Prince Choong Won. Much to his surprise, he meets once again with Lord Jo’s wife.

Gil Dong’s memories are back and he returns home to find that his father is still alive. To prepare for his revenge, Gil Dong goes around looking for his father’s old members. Gil Dong states that he will seek his revenge with Prince Choong Won and that he is ready to be worse than just a thug.

Gil Dong and the gang decide to get revenge on Heo Tae Hak. They are smart about it and plan a way to slowly torture him. Meanwhile, there is a mysterious tension between Gil Dong and Ga Ryung.

Gil Dong and the gang dress up as porters and aid Prince Choong Won on his trip to Hanyang. There, a young lady recognizes Gil Dong as the magical peddler. Meanwhile, Gong Hwa is given the first and last chance to entertain the King.

Gil Dong and the gang plan to separate the bond between the King and Prince Choong Won. They set up a kisaeng parlor and invite Prince Choong Won. Their plan is to gather as much information about him and his followers.

Gil Hyeon becomes a scribe at the palace. The King hears rumors about how a scribe by the name of Kim Il Son has written nasty information regarding the King’s grandfather, King Sejo. Enraged and in order to show his authority, the King demands everyone who is involved in such rumors to be interrogated.

Prince Choong Won is interrogated at the palace. He believes that Gil Dong will prove him innocent, but to his surprise, Gil Dong stabs him in the back. Greatly disappointed, the King punishes Prince Choong Won.

Ah Mo Gae and Gil Dong goes to Geum Ok’s grave. Heo Tae Hak’s men attack Gil Dong and his gang. Meanwhile, the King decides to grant Nok Su her wish.

So Bu Ri makes a mistake, and Gil Dong is forced to meet with Ja Won. Gil Dong and his gang have a fight against another gang in Hanyang. Meanwhile, through the late Lord Jo’s wife, Prince Choong Won meets Jeong Hak’s teacher, Song Do Hwan.

Song Do Hwan decides to help Prince Choong Won and urges Jeong Hak to imprison Kkeut Swe. Meanwhile, Ga Ryung confesses her love for Gil Dong. Teary-eyed, Gil Dong tells her how he truly feels.

Gil Dong tries to turn the table around for Jeong Joon Boo’s case with a story of King Seongjong’s killing his wife for her being jealous. Meanwhile, Jeong Hak finds out that his father was killed by his own servant and that the son, Gil Dong, is the rebel whom he has to catch.

Prince Choong Won and Jeong Hak decide to put Gil Dong into a trap. Choong Won plans to tell Gil Dong that he has killed Uh Ri Ni, and when Gil Dong gets furious and attacks him, they plan to capture and punish him. Meanwhile, Mo Ri realizes that he has regained his strength.

Gil Dong and his men disguise as Hong Chum Ji, and they sweep across the nation, punishing those written in the Hengrok. During their journeys, they also help the innocent, and the people start to love and respect them. Jeong Hak becomes even more determine to catch these thieves. Meanwhile, foreign intruders attack.

Gil Hyeon is appointed by the King to capture the notorious thief, Hong Chum Ji. Unknowingly, Gil Dong is cornered by Gil Hyeon and his men. Meanwhile, Mo Ri attacks two of Gil Dong’s men.

The King opens up a hunting festival and invites his people to watch. To their horror, Gil Dong is brought forward and various hunters attack him. Then, the final hunter, Mo Ri, approaches him.

The King has lost control. In order to show his powers, he punishes whoever conspired to dethrone his late mother. Furthermore, he decides to keep Gil Dong alive and use him as his hunting target.

The King commands the people to hear that Thief Hong is dead. He commands Gil Hyeon to be in charge of recapturing him. Meanwhile, Ga Ryung enters the palace with revenge in her mind.

The King intends to rule Joseon using violence. Gil Hyeon and Gil Dong plan to sneak into the palace and face the King. Meanwhile, Nok Su decides to behead Ok Ran for a trivial mistake.

Hong Chum Ji’s followers break into the palace. The King panics while his men try to protect him. Meanwhile, Jeong Hak finds out Gil Hyeon’s true identity.

The King intends to rule Joseon using violence. People of Hyangjumok are all subject to death because they strongly stand against the King’s will. Gil Dong fights against hundreds of soldiers that are dispatched to kill the people. Meanwhile, Ga Ryung pulls out her hairpin to kill the King.

Gil Dong’s men fight against the royal forces and win. Enraged, the King sends more men to fight against Gil Dong and appoints Jeong Hak to lead them. Meanwhile, Ga Ryung asks the King to come close so that she can tell him the truth about her husband.

Yi Yung orders Ga Ryung to be hung on a pole for Gil Dong to see. Ga Ryung tells Gil Dong that if he surrenders because of her, she will not have it. To everyone’s shock, Gil Dong aims his arrow at her chest and shoots.

As a punishment for losing the battle against Gil Dong and his men, Jeong Hak is forced to become a servant at the palace. Nok Su prepares one last feast for the King. Meanwhile, Gil Dong falls asleep with the unconscious Ga Ryung in his arms.

The people come for the King. Until the end, Nok Su stays by his side. Jeong Hak, now a servant, carries a sickle and confronts his master. Meanwhile, Ga Ryung surprises Gil Dong with news.