A boy arrives at the Southern Catholic Hospital Emergency Center with internal bleeding. Doctor Ham Eun Ho desperately tries to save his life and attempts to stop the internal bleeding. The surgery fails, but miraculously, the boy recovers with the power of a supernatural being. Meanwhile, the police arrest Father Jeong, and the recovering boy disappears.

Eun Ho stops Soo Min from performing an exorcism on Woo Joo and takes him back to the hospital. Certain that Woo Joo is possessed, Father Moon gets consent from the Vatican and convinces Woo Joo's mother that medical help won't help Woo Joo. When they transfer Woo Joo to another hospital, Father Moon and Soo Min take Woo Joo to a place to perform the ritual. Meanwhile, Father Jeong commits suicide in prison.

Soo Min tries to make Eun Ho believe about exorcism. After helping Woo Joo, Soo Min realizes that the evil spirit has moved onto someone else’s body. Eun Ho gets an attack from Mi So, and Father Moon finds another way to defeat the evil spirit. Later on, Father Moon decides to let Soo Min enter Mi So’s subconsciousness in order to help Mi So from the evil spirit.

Soo Min sees his dad in Mi So’s unconsciousness. Eun Ho and Soo Min perform an exorcism on Mi So under Father Moon's control. Father Moon plans that Eun Ho enters Mi So's subconscious through hypnosis and gets rid of the demon. And when being hypnotized, Soo Min sees Eun Ho in a gown.

As soon as they get rid of the devil inside So Mi’s body, a new energumen starts attacking people in the hospital. Ms. Sung gets an attack and Eun Ho sends a footage file of the incident to Soo Min and Father Moon as she finds it strange. Soo Min and Father Moon start finding the new energumen.

The new energumen, Jae Moon runs away from the hospital, and the members of 634 Regia try their best to catch him. Father Moon senses something dangerous and asks Eun Ho to take a leave and stay away from the hospital. Meanwhile, Eun Ho receives a call from her fellow doctor, Tae Hyun, and heads to the hospital in the middle of the night.

After encountering and attempting to exorcize an energumen, Kyung Ran is murdered. Although it was the energumen controlling her body, it looked as if Kyung Ran took her own life. This tragedy causes Detective Koo grave sadness but he is forced to lie in order to hide the existence of 634 Regia.

Do Kyoon feels remorse about what had befallen Kyung Ran, while she as a demon tries to convince him that Father Moon was the cause. When her persuasion fails, she begins to overtake him instead. Yong Pil finds another party in the photo evidence and informs Father Moon that it was the photographer. Father Moon then starts to make his move with the new lead possessed.

Soo Min and Eun Ho are having a meeting with Sister Hae Min who claims to know the way to bring back both of their lost memories but with a risk. Eun Ho decides to participate in the ritual desiring to identify the cause of her lost memories and Soo Min also agrees. In the flashback, Soo Min and Eun Ho first make acquaintance and find more about each other through a volunteer project at a remote island.

Sister Hae Min and Bishop Kwak are discussing the future of 634 Regia following the incidents that led to Ki Sun’s demise. Bishop Kwak suggests its closure but Sister Hae Min disagrees pronouncing that its sacrifices have been greatly beneficial to the religious order. She confirms her conviction with a mention of the message from the Vatican for it to remain. Meanwhile, Soo Min and Mi Yeon continue the efforts in adapting to the reality without Ki Sun.