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.

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.

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.

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.

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.

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.