The thirteenth episode of Moon River commences with a poignant flashback, unveiling the enigmatic past of Han-chul. We witness a younger Han-chul stepping in to shield a woman named Ji-hye from the clutches of unwanted attention from a group of men. This woman, destined to be Queen Jangjeon in later years, shares a moment of tenderness with the young Han-chul, whose noble lineage was once proud but now shrouded in obscurity. Han-chul's unwavering affection for Ji-hye is evident as he asks for her hand in marriage, pending his successful completion of his military exams.
Fortunately, Han-chul emerges victorious, ushering him into the palatial halls where he begins his service. The king, observing his dedication and discipline, forms a bond with him, urging Han-chul to view him as a companion and ally. Han-chul confesses his desire to grow stronger to protect a person dear to him. One fateful day, while out with the king, the latter is injured, and it is Han-chul who escorts him home. There, Ji-hye, who possesses healing abilities beyond the ordinary, tends to the king's wound and captures his heart.
However, the king begins to woo Ji-hye, unaware of her true heart which yearns for Han-chul's affection. The king becomes aware of this and explains to Han-chul that his royal status would provide her with a better shield against the world's ills. Han-chul appears to accept this reasoning and relays it to Ji-hye. In the end, she accepts the king's proposal and ascends to the throne as Queen Jangjeon, eventually giving birth to their sons. However, the dowager queen learns of the prophecy surrounding Je-woon, which foretells of imminent danger to the king's life, and decides to wrongly accuse Jangjeon of adultery.
Han-chul implores her to flee, but she refuses, fearing it would endanger Je-woon. Even the king refuses to intervene. As the time for her to ingest the poison approaches, Han-chul cunningly mixes it with a counteragent and later administers an antidote, saving her life. He hides her away, but when she wakes, she has forgotten him. Han-chul relentlessly presses the king for answers, who stands firm in his decision, asserting his desire to safeguard the throne. At this juncture, Han-chul decides to seek his revenge.
In the present, Se-dol engages in discourse with Yi Hui before visiting Dal-i's family, who coerce him into revealing Dal-i's whereabouts. Soon, even Han-chul realizes that Dal-i is headed towards Gamaksan Mountain. Meanwhile, Je-woon discovers a hidden message in Dal-i's brother's book, scrawled in candle wax. He leaves a message for the crown prince and sets out on his own journey. The message reaches Dal-i (in Yi Kang's body), who learns that Je-woon has found the hideout of the nameless ones and plans to return in three days.
Han-chul is not idle either. He ensures that the astrologers set an auspicious date for the royal wedding in just two days' time! As Han-chul leaves the capital to visit Queen Jangjeon, Dal-i and the king manage to see each other in secret. Dal-i yearns to join Je-woon at Gamaksan Mountain, but Yi Hui counsels her to wait until the eve of the wedding ceremony.
Later, as Dal-i recalls her memory on the mountain with the woman in the white mourning dress, she remembers the woman attempting to give her a letter for the palace, with the word "coup" scrawled on it. This implies she might be in possession of the secret pact! The dowager queen then makes a surprise appearance in Yi Kang's quarters, despite the danger it entails. She informs Dal-i that the left minister's deeds were a revenge for the death of Queen Jangjeon, whose blood is on her hands. She now desires to help bring him down. Dal-i requests the queen to show her a portrait of Queen Jangjeon, and Dal-i recognizes her as the woman she met in the mountains.
In the mountains, Je-woon convenes with Yi Kang (in Dal-i's body) and Shin-won and they set off towards the hideout of the nameless ones. At their hideout, Je-woon and the others spot his mother with Han-chul. Je-woon wants to storm inside, but they stop him. A woman with a scar finds them, but Shin-won overpowers her. Yi Kang recognizes her as Deok-chun from Woo-hee's description. She receives a letter from Woo-hee, informing Deok-chun that her mother had passed away three years ago and that she should escape Han-chul's clutches. Deok-chun reveals that she knows about the royal wedding and that Queen Jangjeon is in possession of something important. Yi Kang, Shin-won, and Je-woon take shelter and devise a plan to save the queen. They are soon joined by Dal-i's parents and aunt, and Hong-nan immediately realizes that Yi Kang and Dal-i have switched bodies again.
As they were pursued, they managed to escape from their hideout. Je-woon, Shin-won, and Deok-chun engaged in a fierce battle against the nameless ones. Meanwhile, Yi Kang deftly distracted the remaining guards and urged Queen Jangjeon to make her way to the docks, where Hong-nan awaited to ferry her to Hanyang. Later, palace guards sent by Yi Hui arrived to lend a hand in overpowering the nameless ones, assisting Shin-won and Je-woon in their efforts.
At the palace, Yi Hui devised a contingency plan. In the event that Je-woon did not arrive on time, he planned to take down Han-chul by confessing to the coup. The next day, Dal-i and Woo-hee donned their wedding attire and were led to the altar. Dal-i washed her hands in a bowl of water, mixing the blood on her hand with Yi Gang’s blood from a piece of cloth. The blood glowed, and once again, the souls swapped. Yi Kang awoke in his own body, rejuvenated and reborn.
Several events unfolded simultaneously. Queen Jangjeon and Hong-nan were near the palace, as were Je-woon and Deok-chun, along with the secret pact they had made. Shin-won and the other palace guards launched an attack on the nameless ones' hideout. And amidst all this chaos, Yi Kang accused Han-chul of killing the late king and prince in front of everyone, his words echoing through the air like a death knell.
In an epilogue, we see Dal-i waking up to find herself captured by the remaining nameless one soldiers, her fate uncertain but her spirit undaunted.
