In Alchemy of Souls Ep 15, Master Lee revealed that he was a soul shifter. He unfolded the story about how his soul got shifted into another young body. It was because of Master Heo, as Master Lee was once meditating for 100 days when Master Heo thought he had died meditating, but Master Lee was testing the new spell by temporarily shifting his soul to another body. Master Heo burned Master Lee’s body, so Master Lee shifted his soul into a child’s body.
Then the scene at the royal palace was drawn where Master Lee revealed that he could find the soul shifters. He told the king that he could not find soul shifters by looking at them, so he brought Gwaju, the wily beast who is inside a dog, as a gift to the king. Listening to this, the queen became enraged at how he could bring such a wily beast inside the palace.
Master Lee asked Lee Jaewook to bring the dog inside, and if he successfully brought the dog inside the palace, he would be rewarded. In the meantime, the queen secretly called Cheonbugwan’s men, who attacked Uk, bringing the dog inside. Jang Wook tried his best to get the dog safely inside the palace. The queen eventually succeeded in convincing the king not to let them bring that wily beast dog inside the palace so that her identity remained hidden.
On the other hand, Mudeok was framed for killing a sari’s village man who knew her identity and some of the thugs who were looking for a swindler, who Park thought was Mudeok. Mudeok ran in order to not get arrested and met maidservant Kim whom she told her the whole story and made her believe that she was not the murderer. She asked Kim to take her to Jinoywon as Choi Yeon was the only one who saw Mudeok at the gambling hotel right before those men were killed.
Mudeok convinced Choi Yeon to tell the truth to the Songrim leader so that she could be spared. Choi Yeon gave her testimony to the Songrim leader of seeing Mudeok at the time the leader entered the hotel, so it could not be possible for someone to kill all those men in that little time. Park Jin believed in Choi Yeon’s testimony, but he didn’t release Mudeok and Jang Wook from imprisonment.
Park Jin asked Jang Wook about Mudeok’s secret, telling him if Jang Wook’s testimony was different from that of Mudeok, then Mudeok would be killed. Park Jin told Mudeok the same, if her testimony was different from that of Jang Wook, then she would be killed. Both Mudeok and Jang Wook understood Jin’s trick and said something that would not let Mudeok be killed. Eventually, they both said the same thing, and Mudeok’s life was spared.
At the end of Alchemy of Souls Ep 15, it was revealed that Jang Wook told Park Jin that he liked Mudeok showing Yang, and Mudeok told Jin that she liked Jang Wook to her death, showing the Yin jade, which convinced Park Jin to release them both.