Carol has to fire two of the nurses. Meanwhile, Gant feels Benton is too hard on him.

Carol will hear whether her suspension is permanent or not. Mark and Doyle do what they can to get a patient with Down syndrome on a heart transplant list.

Jeanie asks Greg to help Al get into a special AIDS-program at the hospital. Olbes brings in her grandfather, who had a stroke.

Carol would like to have a women's and children's health care clinic within the ER. Benton has trouble combining work and fatherhood.

Dr. Corday commits a deadly error after being on-call for nearly 36 hours straight. Peter visits Dr. Kotlowitz and receives encouragement regarding a cochlear implant for Reese. Dr. Amanda Lee, a prospective new ER chief, visits. In the wake of a failed pregnancy attempt, Carol lashes out at a mother using abortion as a means of selective birth control. Carter and Lucy feud when Carter accidentally uses her palm computer and finds out what she thinks of him. Mark panics during a paramedic initation.

Peter accepts Romano's suggestion and takes a two-week job in Minnesota to earn some extra money. Unfortunately, before he gets a chance to leave, he's transferred to backwoods Mississippi, where the hospital is only a two-room building. Peter battles local racism, delivers a difficult infant while battling the grandfather's concerns that the child might be black, and uses unorthodox methods to save two shrimp boat workers. Meanwhile, back in Chicago, Jeanie's condition worsens.

Romano forces Benton to choose between the trauma and cardiothoracic fellowships. Carol worries that she may have lost her child. Corday and Greene bond on the way to a medical conference. Carter mentors an aspiring teenager. Lucy, on a psychiatry rotation, treats an overmedicated foster child. Jeanie finds her faith while treating a reverend.

Carol's pregnancy becomes public knowledge as she learns that she's having twins. Lucy has problems trying to go off Ritalin. Peter learns Carla plans to move to Germany. Kerry finds an abandoned youngster and brings him to the ER. Mark and Elizabeth discuss their relationship. Jeanie and Reggie draw closer again.

When Anspaugh decides to retire as chief of staff and return to surgery, he appoints Romano as his replacement. Greene expresses reservations about the decision, but Weaver does not support Greene. Romano makes Weaver the new chief of emergency medicine.

Weaver tries to save the life of a rape victim while Corday struggles with feelings of disdain as she is forced to save the rapist. Cleo treats a teenage alcoholic boy whose alcoholic mother refuses to recognize her problem or his.

Carter and Lucy are discovered and the staff struggles to save them and go on with normal patient care.

After Corday refuses to perform exploratory surgery on Cleo's patient, Cleo enlists Benton's help, infuriating Corday. Abby cares for a pregnant woman with five children who wants an abortion. Greene lovingly tends to his dying father at home.

As the result of a school shooting, Kovac and Benton care for the gunman and his victims. Abby discovers that Carter has been illegally injecting pain relievers. Greene and Weaver confront Carter about his problem, and Weaver orders him to enter a drug rehabilitation center or leave the hospital permanently.

Dr. Carter struggles with his drug dependency; a custodial strike leaves the ER cluttered with garbage; a riot at a high-school football game leaves several wounded.

Corday rushes through a surgical procedure in order to take off on a romantic weekend with Greene. She is later called back to the hospital after her patient suffers complications. Abby's mother, Maggie, who suffers from bipolar disorder (manic-depressive) and refuses to take her medication, unexpectedly visits Abby at the hospital and wreaks havoc on Abby's life.

Chen gives birth, but insists on breastfeeding the infant before she gives it to the adoptive parents. Greene and Corday consult a brain specialist in New York City who believes the tumor can be safely removed. Stressed and tired, Carter impulsively swallows two painkiller pills but intentionally vomits them. He confesses to Abby.

Benton and Cleo clash over his deceased nephew's girlfriend. They finally agree to call a social worker. Benton confesses his love to Cleo. The spinal surgery malpractice suit is settled by employing a technicality: the equipment used was later recalled by the manufacturer. But Corday now doubts her abilities as a surgeon.

In the series' 150th episode, a massive train wreck mobilizes the emergency room doctors. Corday, Carter and Kovac rush to the scene. Corday falls and injures her back, bringing on contractions in only her 25th week of pregnancy. While amputating the legs of a fallen firefighter, Corday stops because of her pain.

The ER is flooded with foster care home residents, attacked by a shooter bent on tracking down his son, who , with the help of Dr. Green, was put into the foster care system amid allegations he was being abused by his father.

Carter is overwhelmed by patients from a rock concert riot. Benton's former girlfriend is killed in a car accident. Newly promoted to chief resident, Chen panics and misdiagnoses a patient. Kovac angers Abby by flirting with a waitress.

Corday's ordeal, caused by the recent infection-related deaths of several of her patients, worsens when she is closely observed by a stern taskmaster. Corday is outraged when a county investigator accuses her of deliberately euthanizing the patients, who all happened to be elderly.

Benton commits perjury on the witness stand in order to gain custody of Reese. When Romano refuses to give him a more even schedule, Peter resigns and seeks a job at the clinic where Cleo is newly employed. Benton is granted custody of Reese and he and Cleo decide to move to the suburbs together. Meanwhile, Carter's father visits for Christmas with the news that he's getting divorced, Weaver and Sandy Lopez finally go on a date, and Abby catches Nicole in the maternity ward, recovering from an abortion.

As Dr. Greene's brain tumor begins affecting his coordination, he becomes concerned that his fate will be similar to the terminally ill patients he treats.

Just when the ER is understaffed and swamped, two children who were brought in turn out to have full blown smallpox. The entire ER must be locked down. The staff needs to improvise while they battle not only the disease but also frayed tempers.

Dr. Carter, Abby and other staff of the ER are quarantined as the CDC investigate a mysterious, deadly outbreak.

Corday clashes with new surgical resident Paul Nathan regarding his intervention into the treatment of a sickly young woman, Alison, who has signed a "do not resuscitate" order. Abby wonders about the erratic behavior of her visiting brother Eric, and feels conflicted over a nurse's official complaint against Kovac, Abby's former lover. Meanwhile, Pratt comforts Chen after a patient threatens her, and Corday suspects that an unconscious, 14-year-old female patient has been sexually assaulted.

Abby's troubled brother is missing. A car runs into a crowd of teen girls. The alderman with syphilis gives Dr. Weaver a promotion. Dr. Lewis looks forward to a blind date.

The police question Drs. Pratt and Gallant about a rampage at the diner across from the ER. Dr. Lewis befriends her teen admirer, a cancer patient.

Dr. Carter tries to prevent a grieving gang member from going after vengeance. Dr. Kovac races against time to save a Croatian boy's life. A baseball player gets treatment for a heart problem.

Carter returns from Africa, going straight to Abby's bedside. Her response to seeing him is to ask for her key back. She is very chilly towards him all day until new med student Neela Rasgotra answers a phone call for Carter. The message: Luka is dead. Carter decides to go back to the Congo to bring the body back. Neela has a tough first day in the ER, earning Chen's ire after Pratt flirts with her. Gallant, now a full-fledged doctor, helps to show her the ropes.

Ben Hollander is a distraught architect whose degenerating eyesight causes him despondent while a spirited new nurse, Samantha Taggart joins the staff. Elsewhere, disaster strikes when the doctors suspect a mother is abusing her child while Dr. Corday learns something shocking about the charismatic Dr. Dorset, and Dr. Archie Morris is overwhelmed by the chaos and grisly conditions of life in the E.R.

Neela helps treat two Amish teens who were in a car crash. Sam argues with Dr. Kovac when he pays too much attention to her son.

Sam treats an abused, pregnant teen. Dr. Carter introduces African girlfriend Makemba to wintertime. ER chaos shocks a risk-assessment expert. Dr. Pratt and Abby restrain a man who has tuberculosis.

A panic-stricken Weaver is ordered to give her son to the Lopez family. Carter greets the returning Kem, but their meeting with his father, Jack, gets tense after Carter announces plans for his grandmother's estate.

Kovacs stops to help a woman and her son whose car broke down. Steve is getting close to Alex, and Sam panics. Abby is looking for her letter whether to see she passed her boards. Pratt shows off his new Chrysler. Elgin tries to build a connection between him and Pratt. Jing-Mei might be battered by her senile father.

It's a busy Fourth of July and Carter is the only attending working.

A wounded police officer's teenage son must make a life or death decision. Abby tries to convince a girl needing appendicitis surgery to stay at County, but her fathers wants her transferred to another hospital.

Two teens enter the ER with gunshot wounds. When one dies, Neela botches telling the next of kin, making the woman hysterical.

A soccer mom finds herself completely aware of everything going on around her, but is unable to move or speak after suffering a stroke.

Sam's ex-husband shows up and wants to take Alex on a trip. Gallant is back and Neela hopes to see him before he goes back to Iraq.

It's Valentine's Day. Dr. John Carter is back at the County. Brenner and Neela are getting closer. Dr. Banfield is having a hard time trying to have a baby. And Puck and mushrooms may not be a good combination.