Five friends whose friendship goes back to their days in med school are brought back together when a phone call interrupts each of their busy lives.

For the first time in 20 years, everyone's finally working under the same roof. A patient with a familiar name finds Chae Song-hwa.

Yang Seok-hyeong's aloofness frustrates someone on his team. Jang Yun-bok and Jang Hong-do witness a surprising side of Song-hwa outside the hospital.

The hospital's med students are inspired by the doctors, who each look after their patients in their own ways. Lee Ik-jun gets a welcome visitor.

An urgent call sends Song-hwa rushing to the hospital to tend to a young patient. Ik-jun receives a plea from a desperate father.

As life at the hospital goes on, the five friends' growing pains continue. Gyeo-ul is disquieted by frequent visits from a patient's mother.

Jang Gyeo-ul can't get one kind word out of Ahn Jeong-won, who seems especially cold to her. A difficult professor joins the cardiothoracic department.

Kim Jun-wan waits for a response from Lee Ik-sun, who says she needs some time. Jeong-won breaks painful news to the family of his longtime patient.

An unforeseen problem just before a surgery forces Jeong-won to make a tough decision. Meanwhile, Jun-wan is put on edge in the operating room.

Distracted by a problem in his personal life, Do Jae-hak struggles to get through the day. Meanwhile, Chu Min-ha finds herself drowning in work.

Put in a stressful situation, Jae-hak looks to Jun-wan for advice on the right thing to do. Ik-jun accidentally uncovers an extraordinary secret.

Ik-jun handles a sensitive request from the troubled wife of a patient. A sudden piece of news threatens Seok-hyeong's peace.

As doctors and as humans, the five friends each face a maze of life's questions and decisions as they figure out their next steps.

Traveling to and from Seoul, Song-hwa takes on a VIP client in need of surgery. A woman with pregnancy complications fights to keep her baby alive.

An urgent case involving a liver transplant between a father and son is brought to Ik-jun's attention. Jun-wan has big news for one of his patients.

Ik-jun’s team deals with a patient’s anxious brother — and his overbearing attitude. Chu Min-ha leaves a bad impression on a visitor in the cafeteria.

Worries about Ik-sun plague Jun-wan's ever-busy days. While watching over a patient post-surgery, Heo Seon-bin experiences a critical lesson.

A series of tough choices and sudden crises keeps life at the hospital as busy as ever. Through it all, the five friends continue to follow their hearts.

Gyeo-ul receives a disturbing noise complaint about one of Ik-jun's patients. Seok-hyeong opens up to Song-hwa, who gives him a piece of advice.

From student to intern for Yun-bok and Hong-do, and resident to fellow for Gyeo-ul, every step forward comes with plenty of hiccups — and new learnings.

A hospital ping pong tournament brings out each department's competitive streak. Ik-sun and Jun-wan make plans to meet for a proper chat.

One of the hospital's doctors is rushed into the emergency room. A patient with an unanticipated condition poses a challenge for Song-hwa and her team.

Jeong Rosa fears the worst when her memory continues to decline. Song-hwa grapples with the unforeseen diagnosis of a loved one.

The five friends leave for vacation together, but not all of them make it to the destination. Jae-hak and his wife navigate one surprise after another.