Sensing that Ko Seung-tak, a resident at Eunsang University Medical Center, will not get along with him, Cha Young-min, the top cardiothoracic surgeon, plans to get rid of him.

Young-min finds his body in a critical condition and gets confused about if he is alive or dead; Young-min discovers that he can possess Seung-tak only; a mysterious man calls Young-min a coma ghost.

With an emergency patient in front of him, Seung-tak struggles. At the same time, Young-min faces the risk of disappearing for good. The two become physically and mentally inseparable, but neither one seems to accept the situation. Meanwhile, Young-min finds out who the wrongdoer behind Chairman Jang’s case is and gets shocked.

Seung-tak has no other option but to ask Young-min for help in saving an emergency patient. While Young-min is impressed with his good faith, he is also shocked and realizes that there is a possibility that Seung-tak might be seeing him. But first things first, the two team up to save the patient.

Young-min finds out from the ghost patient that the accident he was involved in was also planned out by someone. Meanwhile, Seung-jo begs Seung-tak to do whatever it takes to save him. However, the only doctor who can save Seung-jo is Young-min, and the only person who can connect the two is Seung-tak.

Young-min is excited that he can save someone’s life again. At the same time, Seung-tak asks Young-min what it’s like to save a life all on your own. Meanwhile, someone special to Young-min visits the hospital, not as a guest but as a patient.

Young-min reveals the truth about what happened to Seung-tak 12 years ago; Young-min's assailant regains consciousness but cannot remember anything.

Se-jin feels Young-min's presence when interacting with Seung-tak; Seung-won finds Seung-tak's behaviour suspicious.

Young-min, still in Seung-tak's body, decides to reveal himself to Seung-won; Seung-tak helps Young-min spend some time with Se-jin; something unexpected happens at the hospital.

Young-min feels helpless when the coordination with Seung-jo goes wrong during surgery. Knowing how frustrated Young-min is, Seung-tak looks for other ways to save him. Meanwhile, Se-jin tries to keep a distance from Seung-tak, and Seung-tak is bothered by her sudden change in attitude. After pushing Seung-tak away, Se-jin is alone, and that’s when Min-ho barges in.

Se-jin collapses due to overwork and takes a few days off; Se-jin warns Seung-tak to stay away from Young-min; Seung-won and Tae-hyun hatch another plot.

Seung-tak loses control during his surgery and disappears, leaving everyone at the hospital worried. Young-min learns about Seung-tak's history, and Se-jin's suspicion about Seung-tak grows.

The connection between Young-min, Seung-tak, and Tes is revealed; Seung-tak returns to the hospital, and Se-jin is surprised to see the new Seung-tak.

Se-jin discovers Seung-tak's secret; Seung-tak learns that the surgery has a major side effect; Young-min intends to treat as many patients; Young-min must make a tough choice.

Seung-tak and Young-min get ready for Young-min’s surgery, but Young-min looks like he has a lot on his mind. Either way, this is going to be their last surgery together as one. After the surgery, everyone waits to see if Young-min recovers. However, not everyone wishes that he would wake up or remember what has happened in the past few months.