Created by best-selling author Michael Crichton, this series centers on the medical personnel in the emergency room of a Chicago county hospital. ER tracks the inner workings of County General Hospital, a Level One Trauma Center where heroic doctors and nurses are faced with life-and-death decisions on a daily basis. In its fifth season, third-year med student Lucy Knight joins the team in the ER and kindles a relationship with Dr. Carter, Dr. Corday starts her career over as an intern, Dr. Green watches helplessly as his family is torn apart, Dr. Ross leaves the ER for a new job and the whole time the ER is being run by an imposter!
Lucy Knight, a third year medical student, begins her first day in the ER. Although she impresses doctors with her ability to answer medical questions, her attempts to help patients are clumsy.
To save rent money, Carter lives in a medical student dormitory as a resident advisor. While visiting Corday at her apartment, Benton meets her father. Corday realizes that the only way she can stay at County General is to start over as an intern, which she eventually decides to do.
Greene agrees to serve on the search committee to consider candidates to permanently fill the interim position as chief of emergency medicine. Despite Weaver's objections, Ross gets the job as the new pediatric emergency room attending doctor.
A wounded gang member tries to leave the ER to exact revenge. Benton keeps Reese's hearing disability a secret from his co-workers. Jeanie tells Ross she'd like to be his physician assistant in the pediatric emergency room. Weaver interviews for the job as permanent chief of emergency medicine.
Jennifer plans to relocate to St. Louis and take Rachel with her. Carter places Lucy in charge of the Halloween party at the dormitory so he can do research for his presentation. But trouble occurs when two medical students take drugs with alcohol and almost die.
Greene risks his life to save a teenage male prostitute. Because of the Halloween fiasco, Carter is terminated as resident advisor, and searches for a new place to live.
Frustrated with her inability to conceive, Hathaway confronts a pregnant woman opting for abortion. Weaver derives enjoyment from seeing Anspaugh muddle through as interim chief.
Even though Carter and Lucy constantly bicker with each other, they join forces to save the life of a young girl who desparately needs a blood transfusion. Lucy and Carter search Chicago to locate her father, who is a perfect match for her rare blood.
Since today is the hospital's 100th anniversary, the new chief, Amanda Lee, arranges for Carter to escort a woman, Ruth Johnson who was born 100 years ago today, around the hospital. Lee encourages Greene to supervise a study on a new pain medicine, and he agrees.
On Christmas Eve, Benton refuses to let Romano operate on a patient when it becomes evident that Romano is intoxicated. Jerry thinks that Lee may be stalking Greene.
A curious Greene discovers Lee's a fake and that Anspaugh never checked her credentials. A day care worker suggests to Benton that Reese requires a "special needs" environment because he's exhibiting problem behavior.
Hathaway clashes with Evans, who obtained a grant for a seminar at the clinic without consulting her. Ross jeopardizes a hospital study when he administers an experimental drug to a patient without the hospital's consent.
Corday refuses to testify against Romano after he threatens Benton's career. A harried Anspaugh accepts Romano's offer to serve as acting chief.
Benton takes a costly sign-language class. Romano suggests Benton enroll in a program whereby Benton would substitute for vacationing doctors at rural hospitals for high pay. Part 1 of 2
Emergency personnel feverishly work to save the lives of children involved in a school bus crash. Mobalage's wife suffers from multiple stab wounds. Carter and Lucy refrain from sexual relations with each other due to hospital policy. Part 2 of 2
Benton travels to Mississippi to earn extra money working as a "locum tenens" doctor--a visiting temp--at a rural hospital in a small town. Instead of a hospital, Benton finds a rural clinic run by Maureen (CELIA WESTON), a nurse practitioner and Catholic nun.
While on a ride-along with paramedics, Carter drives the ambulance through a riot to get back to the hospital and accidentally hits a teenage boy. Jeanie is pursued by both Reggie and Dr. Baker. Lucy struggles to convince an Asian family that they should tell the grandmother that she has a fatal tumor. Hathaway decides not to leave with Ross even though she's pregnant.
Weaver visits a woman she thinks might be her biological mother. Later, Weaver realizes the woman cannot possibly be her mother.
Romano forces Benton to choose between two different fellowships. Greene and Corday become better friends on the way to a medical conference. Carter mentors a student.
A terrible storm causes a power outage, and the backup generators fail. The staff frantically works to keep patients alive.
Hathaway finally informs Ross about her pregnancy. She is disappointed when he tells her he won't be returning to Chicago.
Weaver rescues an abandoned, drugged 2-year-old boy. Romano offers Corday the cardiothoracic fellowship that Benton rejected.