After corrupt doctors let his father die, Kang Dong Joo decides to take revenge by entering the medical field himself. As a hospital intern, he meets Doctor Yoon Seo Jung, and the two immediately butt heads.

Seo Jung wakes up having been cared for by a mysterious doctor. Five years later, Dong Joo, a victim of Geosan's familial hierarchy, is transferred to a strange, middle-of-nowhere hospital.

Dong Joo must work quickly with his new colleagues to save Seo Jung. Later, Dong Joo is left to handle the Friday night ER by himself.

Dong Joo reaches his breaking point at Doldam. Teacher Kim receives an offer that he is disinclined to take on.

Dong Joo decides to stay at Doldam to learn more about Teacher Kim. A truck accident brings several critically injured bikers to the ER.

Seo Jung is reunited with a long lost family member. Panic ensues when both Teacher Kim and Dong Joo are away from the hospital during an emergency.

The Geosan staff invades Doldam without notice. The bickering doctors and nurses must work together when multiple emergency patients come through the door.

Teacher Kim is given the choice of saving either Seo Jung or the patient on his operating table, and his dangerous decisions worry the other doctors.

Seo Jung runs away before learning the results of her psych evaluation. Teacher Kim is prohibited from working, and the ER quickly becomes a madhouse.

Seo Jung and Dong Joo happen upon the aftermath of a major traffic accident. The injured victims are brought to Doldam, overflowing the tiny hospital.

Seo Jung learns she is being sued by the drunk driver whose blood she drew at the scene of the accident. Dong Joo is put in charge of a patient on the run.

Dong Joo is faced with a moral dilemma, and he is forced to take a deeper look into himself and what kind of person he's become.

Seo Jung hones her skills, hoping to be chosen for Chairman Shin's surgery team. Dong Joo encounters new patients who may have an extremely serious and contagious disease.

The Doldam staff, patients, and guardians become restless as the MERS scare keeps them quarantined. Chairman Shin's surgery turns out to be a different kind of operation altogether.

Dong Joo feels anxious about his relationship, or lack thereof, with Seo Jung. Another figure from Teacher Kim's past shows up to cause him further trouble.

Yeon Hwa is repeatedly berated by In Bum after listening to Dong Joo over him. Director Do gives Teacher Kim a choice between two conditions if he wants to go through with Chairman Shin's surgery.

Dong Joo and In Bum must perform an emergency operation, but will they finish in time for their part of Chairman Shin's surgery? Or will they lose even more precious time?

The fate of Doldam hangs in the balance as everyone waits for Chairman Shin to wake up, if he does at all. Dong Joo receives some unexpected mail.

With multiple critical patients and an insufficent number of surgeons, Dong Joo worries about the past repeating itself.

An incident at the reception leaves Teacher Kim's future uncertain, and the other doctors anxious. Director Do becomes desperate to keep his title and reputation.