The pilot for the popular TV series is set during 24 frantic hours in the lives of a group of doctors, nurses, and staff members of a busy emergency room at a Chicago hospital. They deal with the seemingly endless casualties that stumble into their place of employment. The central characters are the chief resident and family man Dr. Mark Greene, who is considering a job in private practice due to pressure from his demanding law student wife Jennifer; outgoing Dr. Doug Ross, who deals with cases in his own personal way; straight-arrow Dr. Susan Lewis, trying to get by another long 36-hour shift; inexperienced third-year med student John Carter; cocky surgical resident Dr. Peter Benton; and troubled chief nurse Carol Hathaway.

Mark's wife arrives in the ER with the news that she has passed her bar exams but several members of the staff interrupt their intimate celebration. Greene treats an elderly woman whose husband isn't ready to let her go. It's been eight weeks since Hathaway's attempted suicide, but Doug Ross has yet to bring himself to visit the woman he went out with for two years. Susan Lewis saves a newborn who is brought into the ER choking. She also argues with the psychiatric attending who refuses to admit a patient suffering from dementia. Carter finds himself having to care for a group of German tourists who are suffering from food poisoning. He also treats a young flirt with a rash. Benton treats a recent surgery patient and finds his correct diagnosis overturned by the man's physician. Susan Lewis treats a family struck by a drunk driver. The husband and daughter will survive but there is little hope for the woman. The drunk driver is also brought in suffering from only a few scratches.

Carol Hathaway returns to work after her suicide attempt. Doug Ross still feels guilty about what happened. An ER patient found walking the streets takes to singing, constantly. Susan Lewis has a run-in with the cardiologist on duty, Dr. Kayson, when he disagrees with her treatment of a heart attack victim. At a case review session, she gets very little support from her colleagues. She also treats a woman who is dying of leukemia and who has good advice for Hathaway. Greene treats a woman who has obviously been beaten by her husband but can't get to agree to get help.

Drs. Benton and Langworthy are unsuccessful in reviving a teen-aged boy involved in a traffic accident and it's left to Carter to determine the boy's identity and notify the parents. Unfortunately, he tells the wrong parents that their son is dead. Doug Ross tells a young patient that he will not be separated from his schizophrenic mother knowing that she will likely be hospitalized for a long time. Susan Lewis tells Mark that she is dating the psychiatric attending physician Div Cvetic. She also treats a salesman whose cell phone is having an odd effect on hospital equipment. Benton forgets that he was supposed to sit with his mother while his sister and brother-in-law were to go out for their tenth anniversary dinner.

Mark Greene's wife Jen gets a position clerking with a Federal judge. Unfortunately, it's in Milwaukee, 2 hours away and she wants Mark to look for a job there. Greene and Susan Lewis treat Samuel Gasner, a man who has been waiting for a heart transplant and who will not survive the night unless a donor can be found. John Carter is worried that his latest paramour may have left him with a souvenir of their sexual encounter. Doug Ross treats a young girl suffering from severe asthma but whose mother can't afford her medication. Benton treats Ivan the liquor store owner who is shot for the third time in as many weeks.

The realities of the ER may be too much for a child, but circumstances force Greene to bring his daughter Rachel with him on a day when the outdoor temperature tops 100 degrees and the air-conditioning doesn't work. Benton and Langworthy try in vain to save a boy shot in self-defense. Meanwhile, Lewis's broke sister, Chloe, steals Lewis's TV and VCR. After Ross crosses the line with Hathaway and Taglieri, Hathaway slugs Ross.

Doug Ross' hopes of renewing his relationship with Carol Hathaway take a positive turn after the two of them kiss following a particularly stressful trauma, but his hopes are dashed when she decides to move in with boyfriend Tag. John Carter has a particularly good day when Dr. Green successfully walks him through a complex procedure. Haleh takes Dr. Benton to task when he refuses to act as a role model for a young gangbanger she has an interest in. Benton is also competing with Dr. Langworthy for a prestigious fellowship. It's Susan Lewis' birthday and her sister Chloe shows up at the ER drunk.

Susan Lewis' boyfriend Div Cvetic, a psychiatric resident at County General, seems to be under a great deal of stress regularly lashing out at everyone. Doug Ross takes over for Mark Greene who takes a day off to be with his wife. He has a hard time keeping up with all the paperwork. John Carter is increasingly frustrated with Peter Benton who never seems to invite him to participate in surgeries. Benton learns the result of the fellowship he applied for and his mother shows up in the ER with a sprained ankle. Carol Hathaway treats a patient who was raped. A new ER aide, Bob, start work.

Carol Hathaway faces an ethical dilemma when a patient admits that he, and not his friend, was driving the car that ran a red light and killed a pedestrian. She decides to tell Tag about kissing Doug Ross. It's Thanksgiving and the doctors treat an animal rights activist who was attacked by the turkey he was trying to save. Doug Ross is going to the Bahamas with Linda Farrell and he is very much feeling like a kept man. Carter has to treat a transgender woman who has now reached an age where she can no longer pass as a woman. Carter's indifference is the final straw. Susan Lewis continues to worry about Div Cvetic, whose condition seems to be worsening.

The ER staff's slow snow day becomes chaotically hectic when the casualties of a 40 car traffic accident flood in.

It's Christmas-time and the expected range of emotions is to be found among the ER staffers. Susan Lewis treats a middle-aged woman who is overjoyed at finally getting pregnant. Susan is also shocked to hear that her boyfriend Div Cvetic has quit his job and moved out of his apartment. Mark Greene treats a young drowning victim. Doug Ross takes Greene's advice and decides to tell Carol Hathaway that he loves her; unfortunately he chooses to do so at her engagement party. Peter Benton jumps the gun and arranges for transplant teams to harvest an accident victims organs but the man's wife is now refusing to give consent. Susan's sister Chloe announces that she is pregnant.

Susan Lewis has a run-in with Dr. Jack Kayson, the cardiology attending, when he accuses her of not providing him with all necessary information on a patient who subsequently died. He makes it very clear that Susan will bear all responsibility for his death. Her sister Chloe informs her that she and her boyfriend are moving to Texas. John Carter is still frustrated by Peter Benton's apparent lack of interest in teaching him anything but a new go for it attitude leads to an invitation to assist in a surgical procedure. Benton's sister suggests to him that the time has come for them to put their mother in a care home.

Benton is called out of surgery to find his senile mother.

Dr. Kayson becomes Lewis' patient.

Dr. Greene gets offered a new job by Morgenstern.