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

A busy Dr. Greene goes all day in solving his patients' problems until he encounters the case of a pregnant woman suffering from complications that threaten both her life and her unborn baby's.

In the middle of a torrential rainstorm, Dr. Ross stumbles across a child trapped in a drainage pipe rapidly filling with water. Doug does everything possible to save the boy, Ben Larkin. Harper develops a bond with a young girl with separated parents.

Dr. Greene and Corday bond with their parents, Lucy cares for a patient with a psychotic break, and Valentine's Day celebrations in the ER end tragically for one of the students.

Dr. Greene's final days are spent in Hawaii with Rachel, teaching her to drive and surf. When he suffers a seizure, Elizabeth is called. Mark refuses to go home. He manages to make amends with his daughter before his eventual death.

On Thanksgiving Day, a helicopter crash outside the ER leaves several injured, and kills Dr. Romano. Alex tries to bring Sam and Luka together.

Because of benzene that's been spread, the ER has to close. Weaver gets felled and Carter has to take the lead.

After some staff members are caught going through a dominatrix's bag, Weaver makes them attend a sexual harassment seminar, where they learn about each other.

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.

While out for a mind-clearing run, Banfield encounters a desperate situation and finds herself trying to rescue a young girl from drowning in a nearby lake. Painful memories of her son in mortal danger and Dr. Greene's heroic attempts to save him are triggered during the experience. Meanwhile, Gates attempts to pull some strings to help out a homeless war veteran, and the interns continue to struggle in the ER.

The last 44 minutes of ex-con & alcoholic Charlie Metcalf's life are in the ER, as he slowly succumbs to end-stage liver failure.

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.

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 reads a letter from terminally ill Dr. Green to the ER staff. Dr. Weaver lashes out at a mentally challenged patient. A terminal, homeless man continues asking for Dr. Green.

Casualties of a disaster flood the ER, which is short-handed because everyone is at Dr. Carter's going-away party because he's leaving the ER after 11 years. Dr. Pratt looks for the courage to confront his father, Charlie.

Chaos reigns in the ER when two prisoners are brought in for treatment, but instead plot a violent escape. Their desperate actions place one doctor in harm's way, and forces one nurse to become a tool in their plan.

A severe blizzard leaves the ER utterly devoid of patients, leaving the staff free to goof off. In the middle of their fun, a call comes from dispatch, informing the ER of a 40-car pile-up with dozens of casualties. The ER goes from being deserted to capacity. All surgeons are called in. Bob surprises everyone with a quick and life-saving decision. A new doctor, Angela Hicks, arrives just at the right time. Ross and Linda return from the Caribbean just as Carol makes a surprise announcement.

Shep and Raul respond to a massive fire without proper equipment, risking their lives to save addicts and their children. Shep will be okay, but Raul has third-degree burns covering his body; it's only a matter of time. The ER is flooded with burn victims. Chloe returns to Chicago. Doug is stood up by his father for a basketball game.

Mark finds himself manning a very crowded ER on his scheduled night off, filling in while Doug is out with whiplash and Susan meets with her lawyer. He tries to juggle hunger pangs, 40+ patients in the waiting room and a never-ending stream of traumas.

Greene prepares to bury his father. Chen worries about Carter's mood swings. After witnessing the interaction between a dying woman and her family, Hathaway realizes she wants her family together and flies to Seattle to join Ross.

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.

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.

Greene confronts Corday when she orders Rachel out of their home; Abby tries to protect a battered neighbor who refuses to press charges against her husband.

John Carter returns to the Congo to retrieve Luka Kovac's body. He finds however that the area where was killed is still too dangerous to enter. He and Gillian finally manage to hitch a ride with a Red Cross worker, Debbie, who is going to the area. In flashbacks, we learn how Kovac and his fellow aid workers were taken prisoner by rebel troops. They are shot, one at a time, until only Luka is left. Amid the destruction of the eastern Congo, we learn his fate. Carter also makes a fateful decision.

Carter takes Kem to the hospital to check on their baby since it's not kicking anymore.