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.

Kayson, a married man, tries to start a romance with Susan by asking her to dinner. Deb unknowingly eats LSD-laced chocolates. Carol takes an interest in a Russian girl abandoned in the ER.

It's a day of birthdays. Peter Benton's mother is celebrating a birthday and he tries desperately to find someone to cover his shift. He makes a choice however when Dr. Hicks suggests that he's been absent too often and may wish to consider a leave of absence until his mother's situation is resolved. Carter thinks it's Benton birthday and has a surprise for him. Mark Greene's daughter is also having a birthday but he misses that due to an emergency at the hospital. An elderly, solitary man in the final stages of cancer arrives in the ER on his birthday. Carol Hathaway suggests to her fiancé that they adopt little Tatiana, the AIDS patient abandoned in the ER. Ross has to deal with a young child who was kicked out of a window.

Carol Hathaway goes ahead with her plans to adopt Tatiana, but her past history makes her ineligible. Benton continues to trade shifts so he can spend time with his mother but it all catches up with him and he has a run-in with Dr. Hicks. Doug Ross treats an abused child. Green, Benton and Carter take extraordinary measures to save a man they later learned had signed a DNR. A consultant arrives to study procedures in the ER, but all is not quite what it seems. Mark Green's wife Jen has an important announcement. Benton's mother has a serious accident when he falls asleep on the couch.

Dr. Benton has to deal with the aftermath of his mother's fall and crosses the line with the surgical attending when he insists on scrubbing in for her operation. Dr. Greene deals with Jodi O'Brien who is two weeks away from giving birth. With the obstetrics attending unavailable, he decides to try to deliver her baby in the ER, with tragic results.

Dr. Greene is still haunted by the death of Jodi O'Brien and isn't sure he can function as a doctor. At Susan's urging, he takes the night off but unfortunately for him, the new head of the ER Dr. 'Wild Willy' Swift arrives unannounced. Susan impresses Swift with her handling of many cases on a busy night. She also has to deal with the case of a young man who has had the hiccups for two days but may in fact be suffering from something far more serious. Nurse Hathaway and fiancée Tag are still working out the details of their wedding. Peter Benton's mother is still hospitalized and he will not accept that her age and her injuries mean that she will need permanent nursing care. Dr. Ross is now dating Diane Leeds. John Carter and Deb Chen's attempts at oneupmanship is starting to take on ridiculous proportions.

Dr. Greene is still having trouble dealing with cases in the ER and the new Chief of the ER is growing increasingly concerned. Greene also faces a difficult peer review to examine his handling of the Jodi O'Brien case. Dr. Benton takes on the difficult task of telling his mother that she must be placed in a home with full-time care. Susan's very pregnant sister Chloe returns to live with her. Dr. Ross deals with the case of a young girl with a heart condition while Ross and Carter encounter a patient who refuses treatment for tuberculosis. When Benton asks Deb Chen and Carter to submit their procedures book in a few days, Deb feels she has to get a few more procedures under her belt if she's to best her fellow student. Unfortunately, her eagerness leads to near tragedy for a patient.

Greene finds his marriage falling apart and is concerned at how little time he's spending with his daughter. He also treats an eight week old child with a heart murmur who requires surgery. Susan tries to get her pregnant sister Chloe to take her pregnancy seriously, but her head isn't quite into it. Benton tries desperately to find a surgeon who will operate on a 16 year-old with a severe brain aneurysm that could burst at any time. He's also concerned at his mother's care and is growing ever more attracted to Jeanie Boulet. Doug Ross' commitment to Diane Leeds gets more serious when he agrees to be an assistant coach for her son's little league baseball team.

Doug Ross and Nurse Hathaway treat a girls' basketball team from a local catholic school for meningitis. Their teachers also need to be tested but one of them confides in Hathaway that she may have a particular problem. Green and the Chief of Staff have a disagreement in the middle of a procedure. With the wedding only two weeks away, Tag and Carol Hathaway have to deal with all of the final preparations, not the least of which is writing their own marriage vows. Susan deals with a suicide victim who is using emotional blackmail to keep his girlfriend from leaving him. Susan reaches the breaking point with her sister Chloe and tells her she has to move out.

On a fateful Mother's Day, several staffers in the ER face possible life-changing events. Susan Lewis' sister Chloe gives birth to a beautiful - and healthy - baby girl. Things start to go wrong however when their mother Cookie - who had agreed to take in Chloe and the baby - suddenly decides she's done enough and Susan will have to take care of it. Carter turns down an offer for an ER sub-internship in the hopes that he'll get an offer in surgery. Dr. Hicks has news for him however. Benton's mother takes a turn for the worse. Carol Hathaway is overwhelmed with the final preparations as her wedding day approaches.

It's Carter's last day in the ER and finally fed up with Dr. Benton's apparent indifference, rejoices when he learns that he gets to write an appraisal on him. He subsequently regrets his negative input when he gets offered the surgical sub-internship he'd hoped for and learns that Benton gave him a glowing appraisal. He also spends a good part of the day with young leukemia victim who is fed up with life. Benton and Jeanie Boulet's relationship reaches a crossroads. Mark Greene is offered an attending position at the hospital but also learns that he is being sued for malpractice over his handling of the Jodi O'Brien case. The big day for Carol Hathaway and Tag is here but doubts creep in and one of them gets left standing at the altar.