When mysterious ghosts attack the royal palace and the Crown Prince, King Haejong must battle an evil tribe and a monstrous serpent to save his son.

King Haejong manages to save the shaman and save his son, but he brings an evil force back with him to the palace.

12 years pass and Prince Wolgang is living outside palace walls, seemingly unfocused and carefree about the life that he leads. Meanwhile, Do Ha makes her way to the capital in search of her sister.

Haunted by his nightmares, Kisan calls back Sadam to help him with his Taoist powers. Wolgang is continually followed by three friendly ghosts even though he does everything he can to ignore them.

Prince Wolgang sets the test for shamans to enter Sogyukseo, but in doing so puts himself in the king's line of fire.

Do Ha needs to find a job so that she can pay for her lodging. An assassin, seemingly sent by the king, comes after Prince Wolgang.

The hunt is on for Prince Wolgang, who now believes that everyone has abandoned him. Sadam uses Do Ha to help him locate the dragon god.

Wolgang tries to find out who tried to kill him. Sadam tries to maintain power over the king by setting ghosts to wreak havoc on the capital.

The Prime Minister comes up with a plan to help Wolgang clear his name. We learn more about the backstory of Jo Sang Heon, the blacksmith.

The King comes up with a plan to make the Prime Minister and Prince Wolgang attack each other politically. He begins to lose his trust in Sadam, who resorts to desperate measures to regain his influence.

Sadam calls on the goddess of smallpox to wreak more havoc in the capital. Soo Ryun is arrested, and it drives Wolgang and Moo Seok further apart.

As smallpox spreads unchecked, the king's authority is threatened. Sadam pins the blame of the smallpox epidemic on Wolgang.

When Moo Seok's sister becomes further entwined to the goddess of smallpox, he is propelled to join the Night Watchmen and stop the goddess before she attains her ultimate goal.

The newly formed Night Watchmen try to stop Sadam from resurrecting the monster serpent when construction begins on a pagoda that will aid the serpent to ascend to the heavens.

Wolgang tracks down Handmaiden Kim to find her side of the story and see why his mother died. Sadam's hold over Yeon Ha weakens.

Sadam attempts to control Prince Wolgang using the same ghost that he cast on Wolgang's father so many years ago.

The Night Watchmen have a plan to take down Sadam, but they've greatly underestimated their foe. Meanwhile the king's split personality becomes an issue when the darker side takes control of the king's body.

The Night Watchmen discover a doppelganger in their midst and embark on a mission to undo Sadam's spell. Kisan's demands to build the temple faster takes a toll on the people of Joseon and his court.

Yeon Ha's soul is so corrupted that she begins to wreak havoc on the palace, and not even her sister can save her. Soo Ryun takes over Maeranbang in an attempt to ensure her future as Wolgang's wife.

The Prime Minister attempts to overthrow the monarchy with the help of Sadam and his evil ghosts. Moo Seok's loyalties are tested when he is forced to choose between the Night Watchmen and the King.

Sadam and Soo Ryun manipulate Do Ha to get what they want from her, but their own interest conflict with each other. Wolgang does everything he can to save Moo Seok from the underworld.

Wolgang locates the sovereign seal that determines the rightful heir to the throne. He attempts to ally with the king, but is the king to be trusted?

Sadam forces the Prime Minster to go insane to serve his own nefarious ends, and traps the Night Watchmen into handing over the sovereign seal.

The Night Watchmen must defeat the serpent god in hell and destroy Sadam once and for all to restore peace in the kingdom.