In the sixth episode of "To My Beloved Thief," the story unfolds with Eun-jo discovering that Prince Yi-yeol had already known her true identity as Gil-dong. A flashback reveals that on the night of the switch, Prince Yi-yeol saw the mask and arrows tossed into the well, connecting the dots. He was not surprised to encounter her near Gil-dong's grave since both of them were suspicious about the fake Gil-dong.
The person responsible for setting up the fake Gil-dong appears to dig the grave. Eun-jo notices that the man has a scar on the back of his hand. Officer Park brings two of Eun-jo's friends to see Gil-dong's grave, and the culprit runs away. They pursue him, but he escapes.
Prince Yi-yeol speaks honestly to Eun-jo about his feelings regarding her being Gil-dong. He admits that he understands why she had to steal to help the slaves, but also warns that she is not to steal ever again, not while he is in her body or after they switch back. He warns that he will have to arrest her.
Trouble brews for Eun-jo in her in-laws' house when Seung-jae spots her with Prince Yi-yeol that night. He confronts her in front of Secretary Im, aiming to humiliate her. Prince Yi-yeol, still trapped in Eun-jo's body, cleverly explains that she was with her younger brother Dae-II.
Prince Yi-yeol knew that Seung-jae would not have made such accusations if he had seen the man's face. Since he is an official, he must know Prince Yi-yeol. He warns Jae-I against using belittling and insulting language with Eun-jo. However, he gets triggered when he mentions that Eun-jo was involved with a man. He stands up for Eun-jo, reminding the in-laws that since she married the grandfather, her seniority is above theirs, and she deserves basic courtesy.
Meanwhile, Hae-rim has not had time to bring up the broken engagement with her brother. Jin-won gives her some herbs to send to Jae-I, her fiancée.
At the palace, Eun-jo, now inhabiting the body of Prince Yi-yeol, pays a visit to the Queen Dowager. Her meticulous care for her arouses some suspicion, and she makes a request to see Hong-si, the new court lady in the Grand Prince's palace. In reality, Hong-si is actually Prince Yi-yeol, who had earlier disguised himself to assist Eun-jo in facing the Queen Dowager. This request sends Eun-jo into a panic, and she scurries around with Dae-chu in search of Hong-si. She finds him waiting to meet Dae-II with her mother. It turns out that he wanted to inquire about the man Jae-I had mentioned.
Eun-jo's mother is bewildered by the interactions between Eun-jo and the young master who has just entered their home. She tries to instill respect in Eun-jo's speech, but she explains that they are only acquaintances. Upon learning that the Queen Dowager is seeking out Hong-si, he asks to leave. Before leaving, her mother retrieves the silk shoes that Eun-jo had carefully stashed away during the wedding. Prince Yi-yeol realizes that she treasures his gift, taking the opportunity to tease her. As he departs, Eun-jo, now in Prince's body, warns her mother to minimize her interactions with her daughter.
Meanwhile, Prince Yi-yeol is thrilled that the switch has occurred, stating that he feels like he's on a scavenger hunt, slowly uncovering all the things Eun-jo had hidden from him. At the palace, they run into Secretary Im and Seung-jae. They inquire about the medicine and suggest questioning the royal physicians. Eun-jo almost forgets whose body she's in and bows down to them, but Prince Yi-yeol gently taps her to regain her composure. As they walk away, Secretary Im almost discovers that the court lady is Eun-jo, but Dae-chu steps in to save the day.
As Hong-si, Prince Yi-yeol visits the Queen Dowager, where Eun-jo questions Secretary Im about the herbs used in His Majesty's incense. After earning the Queen Dowager's trust, Hong-si is tasked with closely monitoring Prince Yi-yeol, particularly his interactions with women.
Later, Prince Yi-yeol falls asleep in his chamber, complaining that walking in Eun-jo's small body is exhausting. When he wakes up, they have an honest conversation about why Eun-jo decided to become Gil-dong. It was mainly because she hated seeing ordinary people so malnourished that the medicine they gave at the Hyeminseo no longer worked. She promises that if she ever gets caught, she will make sure it's Prince Yi-yeon who arrests her. Eun-jo then tells Prince Yi-yeol about the strange medicine, and he decides it's worth looking into.
Meanwhile, Secretary Im and Seung-jae feel that Prince Yi-yeol is becoming an obstacle to their plans. They start scheming about how to get rid of him. At the same time, His Majesty can no longer withstand the withdrawal symptoms and asks Geum-nok to light the incense. Secretary Im doesn't want Seung-jae involved in the scheme against Prince Yi-yeol, so he has Jae-I posted at the State Tribunal. He tasks him with going through all the cases handled by the police bureau, looking for something they can use against Prince Yi-yeol. He finds notes indicating that Prince Yi-yeol protected Gil-dong from getting arrested.
Meanwhile, a mysterious organization emerges, investigating Gil-Dong's death as people hold his memorial. In the meantime, Jae-I lurks around the palace waiting to capture Prince Yi-yeol. He discovers Eun-jo and drags her out. They run into the Grand Prince, who just helped Hae-rim out of a tricky situation where other noble ladies were humiliating her for the broken engagement. Eun-jo, in Prince Yi-yeol's body, wants to help her, but she asks him not to interfere. She states that it would only make things more complicated. In the end, Jae-I drags the person he thinks is Eun-jo home.
Later, Prince Yi-yeol, in Eun-jo's body, confronts Jae-l for his possessive behavior. It is at this point that he realizes that Jae-I has feelings for Eun-jo. His eyes show desire and genuine concern hidden behind insults and humiliation. He warns Jae-l to tread carefully. Just then, a soldier informs Jae-l that he's being summoned by his dad.
Meanwhile, Eun-jo at the palace is restlessly worried about Prince Yi-yeol. Dae-chu tells him of all the ways her in-laws will punish her for going to the palace. It turns out the prince secretly helped to keep Eun-jo safe on her wedding day. Upon realizing how much the prince cares for her, she finally gives in and asks Dae-chu to bring the horses.
At the end of the episode, a member of the mysterious organization corners Eun-jo (Prince Yi-yeol). He holds a sword to her throat and asks if she is Gil-dong. Meanwhile, Jae-I stops Prince Yi-yeol (Eun-jo) with state tribunal officials to arrest him for helping the murderer Gil-dong escape. At this critical moment, the bracelets start glowing, and they switch back to their original bodies instantly. Relief lasts a few seconds as Prince Yi-yeol realizes that the real Eun-jo might be in danger and rides out to find her.
