The film focuses on doctors and four first-year residents working at Angels Memorial Hospital emergency room and treating patients under difficult conditions. They are including the ER Residency Director Dr.Leanne Rorish, the ER attending physician Dr.Neal Hudson, four first-year residents Dr.Christa Lorenson, Dr.Malaya Pineda, Dr.Angus Leighton and Dr.Mario Savetti, besides there are an ER attending physician Dr.Rollie Guthrie, and a senior nurse Jesse Salader.