Queen Dowager Cheonchu wishes her own son to become the next crown prince. However, Mokjong is not happy with how Kim Chi Yang, the Right Senior Executive, and Queen Dowager are trying to take over his place as he is determined to succeed the throne to King Taejo's descendant. Therefore, Mokjong is about to summon Prince Daeryangwon back to the palace, while Kim Chi Yang and Queen Dowager secretly send assassins to murder him.

Court Lady Choi threatens Prince Daeryangwon to take the food Queen Dawager has prepared for him. Prince Daeryangwon quickly runs away from the temple and hides himself in Mount Samgak. Court Lady Choi orders the men to burn down the mountain to find him. Meanwhile, Mokjong holds a banquet for his people, and Kim Chi Yang plots a crime for the night.

Kang Jo, Northwest Temporary Government Officer, sets off for Gaegyeong with a crucial mission. However, deep within his thoughts, he grapples with the realization that Goryeo's very existence is at stake if the current state of ruling persists. Meanwhile, in another part of the kingdom, Prince Daeryangwon anxiously awaits assistance from His Majesty. To his surprise, he finds himself confronted with an entirely new chapter of life, carefully orchestrated for him.

Caught in the crossfire between those gearing up for war and those working to prevent it, the puppet king, Wang Sun, and Kang Gam Chan form the front line of those seeking to avert conflict. On the opposing side, Kang Jo believes in the inevitability of war and sees it as a chance to eradicate the Khitans. The turning point comes when envoys from Khitan arrive with a message poised to alter the course of history.

The ministers struggle to dissuade the Khitan envoys as Prince Daeryangwon expected. He believes that Khitan is using the Palace Head Secretary's treason to justify the war. Therefore, Prince Daeryangwon summons Kang Jo alone to his chamber at night to get rid of him.

Details The battle between Goryeo and Khitan begins in the middle of the night, and the people of Goryeo shiver with fear. With 400,000 soldiers, Khitan attacks Heunghwajin for seven days straight, but they are unable to destroy the fortress. Therefore, they come up with another strategy. Meanwhile, Prince Daeryangwon visits the temple where people are gathered to pray.

The Emperor of Khitan is infuriated as he loses the first conquest expedition he is leading. He starts advancing south with his army towards Samsuchae to destroy Goryeo's main force. Therefore, even though Officer Yang manages to defeat Khitan soldiers, the main force assumes Heunghwajin has lost the battle as they are trapped. Officer Yang must find a way to send the word.

The spearhead commander of the Khitan army launches an attack and captures Kang Jo. The emperor of Khitan threatens Kang Jo and the captured generals to become vassals of Khitan. Meanwhile, Hyeonjong receives the news that the Goryeo army was defeated, and Deputy Minister Kang advises him not to share the news with the people.

Hyeonjong sends Deputy Minister Kang to Khitan's camp as an envoy to relay his message. However, the commander of Khitan's army does not trust his words and decides to hold him back in their camp. Furthermore, Deputy Mayor Won of Seogyeong Fortress gives up on fighting against Khitan and is about to surrender.

As the Khitans advance southward, Kang Gam Chan urges Wang Sun to consider a strategic withdrawal for a greater purpose. Wang Sun's unwavering loyalty to his people clashes with the stark reality of limited options. With Gaegyeong in the crosshairs, Wang Sun stands on the precipice of a crucial decision.

Kang Gam Chan makes a critical decision to stay back in Gaegyeong, sacrificing himself to create a window for Wang Sun's escape. Despite Kang Gam Chan's noble sacrifice, Wang Sun encounters unforeseen dangers at every step of his journey. Meanwhile, Yang Kyu is devising a plan to reclaim Gwakju, the current base of the Khitan army.

The realization of the hardships encountered by those south of Gaegyeong leaves Wang Sun with a sense of emptiness. The difficulties they face highlight his shortcomings as a king, evoking a deep sense of disappointment in himself. Meanwhile, Kang Gam Chan finds himself in captivity as he attempts to secretly rendezvous with Xiao Paiya.

As his people turn against him, Wang Sun bears the weight of shame for not living up to their expectations as their emperor. Entrusting them with his fate, he seeks to ease the suffering of his people. Ha Gong Jin, following Kang Gam Chan’s plans, heads toward the heart of the Khitan army with a diplomatic letter.

Upon reaching Gongju, Wang Sun receives a warm welcome from Kim Eun Boo, the governor, and one of his daughters. Wang Sun discerns a hidden agenda in the daughter's intentions but soon recognizes her potential as someone crucial for Goryeo in these challenging times. The Khitan army begins withdrawing from Gaegyeong, prompting Yang Kyu to seize the moment and launch an attack.

Yang Kyu throws himself into the Khitan army to rescue prisoners, fully aware that this might be his last battle. As expected, he and the remnants of his forces find themselves pitted against the Khitan army in overwhelming numbers. Meanwhile, Wang Sun receives news of the Khitan army's retreat and hurries back to Gaegyeong. Witnessing the state of Gaegyeong, he falls to his knees in despair.

In the face of opposition, Wang Sun remains unwavering in his commitment to overhaul the core issues haunting Goryeo, aiming to fortify the nation and spare his people from the ravages of war. Nevertheless, dissenters argue that certain priorities must be addressed before delving into Wang Sun's proposed changes. Meanwhile, the Khitans are gearing up for another confrontation with Goryeo.

In the face of strong opposition, Wang Sun persists in pursuing his goals, alongside Kim Eun Boo. Kang Gam Chan, while sharing Wang Sun's ultimate objective, disagrees with his approach and goes to great lengths to persuade him otherwise. Eventually, Wang Sun remains unwavering in his convictions and removes Kang Gam Chan from his position. To curb Kim Eun Boo's influence on Wang Sun, Kang Gam Chan implements assertive actions.

The queen consort seeks to punish Kim Eun-bu while the king is away from the palace. But guilt leads Kang Gam-chan to attempt to spare the commander.

With Kang Gam-chan's help, Wang Sun succeeds in launching reforms. However, the local governance is unhappy, and Kang Gam-chan faces the consequences.

Wang Sun puts his life on the line during an intense confrontation with regional lords to bring about reform in Goryeo's regional domain. With Kang Gam Chan's return to the royal court, Wang Sun secures a reliable ally. Concurrently, the Khitans exert pressure on Wang Sun to fulfill the homage promised during the recent war.

The Khitans demand that Goryeo cede its territories to prevent another war, turning a tribute issue into a crucial decision for Goryeo. With time running out, conflicting opinions emerge, and amidst this urgency, Kim Eun Boo takes a perilous gamble for a daring escape.

Wang Sun prepares for battle while Kim Eun Boo, risking his life, attempts to provide Wang Sun with updates on the Khitans' situation. Meanwhile, during this critical moment, military officials in Goryeo decide to oppose Wang Sun's orders, insisting on the restoration of their rightful authority. Kang Gam Chan departs for Heunghwajin with the orders issued by Wang Sun.

On the edge of the northeastern border and lacking battlefield expertise, Kang Gam Chan encounters a looming confrontation with the unyielding Jurchens. Meanwhile, Wang Sun overlooks the insubordination displayed by military officials, while the brewing anger and rage inside Kim Hoon and Choi Jil persist.

Amidst Goryeo's financial struggles, Kim Hoon and Choi Jil launch a rebellion, citing the seizure of military officers’ properties as their justification. Wang Sun, lacking sufficient guards for protection, finds himself surrounded by his own forces. Meanwhile, border troops mobilize toward Gaegyeong to aid Wang Sun.

Kim Hoon and Choi Jil threaten the lives of Wang Sun's vassals, compelling him to order the soldiers heading to Gaegyeong to retreat. With circumstances turning against Wang Sun, he faces a dilemma, torn between doing what is right and safeguarding his innocent vassals. Meanwhile, Kang Gam Chan and other vassals operate in the shadows, clandestinely searching for the mastermind behind the rebellion.

Wang Sun successfully pursues and apprehends Park Jin, but he is constrained by his own lack of authority. He subsequently seeks to persuade Kim Hoon, who is engaged in a dispute with Choi Jil, to quell the uprising. Meanwhile, a second envoy from Khitan returns to Goryeo, demanding that the King of Goryeo pay tribute to prevent hostilities.

The vassals, having received Wang Sun's directives, ready themselves to suppress the rebels at Seogyeong. Although Wang Sun, accompanied by the rebels, eventually reaches Seogyeong, those expected to execute his commands are conspicuously absent. Nevertheless, there may be an undisclosed scheme underway to prevent Wang Sun from crossing the Yalu River.

Wang Sun eradicates the rebel faction and prepares for war against the Khitans. In 1018, the final and decisive battle between Goryeo and the Khitans draws near. With Kang Gam Chan leading the Goryeo army as its commander, they embark on their journey toward the ultimate confrontation.

The Khitan Army's maneuvers raise suspicion as they actively evade engaging with the Goryeo forces and persistently advance solely southward. Recognizing their strategic intent, Kang Gam Chan advises Wang Sun to consider seeking refuge, but Wang Sun adamantly issues strict orders to defend Gaegyeong.

Accompanied by his remaining soldiers, vassals, and the people of Goryeo, Wang Sun ventures beyond the fortress boundaries with the intention of minimizing the suffering of his people. Meanwhile, Kang Gam Chan clashes with the retreating Khitan forces on the plains of Kwiju, marking the onset of the war.

The culmination of the war sees Goryeo emerging triumphant over the Khitans. Kang Gam Chan's return is a scene of jubilation, with the citizens of Gaegyeong celebrating his victory. Yet, Wang Sun, undeterred by the momentary glory, devises a plan aimed at ensuring enduring tranquility in Goryeo.