The ER is quarantined when a viral outbreak jeopardizes the lives of the doctors and patients at Angels Memorial. Also, Ariel, the young girl Leanne bonded with a year ago when she lost her father, returns to Angels.
In the busiest, most notorious ER in the nation the staggering influx of patients can outweigh the limited resources available to the extraordinary doctors and nurses whose job is to treat them all - creating a condition known as Code Black. At the heart of the ER's controlled chaos is Residency Director Dr. Leanne Rorish, renowned for successfully performing high-risk procedures in Center Stage, the trauma area reserved for the most critical cases.
Her four new first-year residents are Christa Lorenson, Malaya Pineda, Mario Savetti and Angus Leighton. Leanne's confidante, Jesse Sallander, is an amiable seen-it-all senior nurse who manages the residents. Also working in the ER is Dr. Neal Hudson, an excellent physician who sometimes disagrees with Leanne's 'cowboy' approach, and Dr. Rollie Guthrie, the energetic, longest-serving attending. In Center Stage, life is measured in seconds, and these heroic doctors and nurses operate with speed and skill within an overwhelmed system to treat the crowds of people who are often there for one of two reasons: to die or to receive a life-saving miracle.