Weaver returns to the emergency room after a self-imposed sabbatical of three weeks, wondering how her newfound lesbian identity will affect her workplace relationships. Having purposely allowed a mass murderer to die, Greene must keep the secret amidst the scrutiny of his superiors.

Peter Benton continues his court fight against Reese's stepfather, Roger, who seems to have the upper hand. When a woman is accidentally shot during a gas station robbery, Dr. Corday tries to convince the husband to let them harvest her organs. A 15 year old boxer is brought in with a head trauma after sparring with his older brother. Newlyweds are having trouble when she constantly breaks out in a rash; Carter thinks he knows the cause.

An injured and condemned murderer wants to die in the ER rather than await execution; Abby advises a neighbor to seek shelter from her abusive husband.

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.

Weaver makes a mistake on live television while demonstrating flu shots, inadvertently sticking two reporters with the same needle. In the bathroom later, Susan and Abby catch Weaver in a stall with a needle. Weaver confesses to Susan that she's taking hormones. Carter, assuming Susan knows already, tells her about Abby's drinking problem. Abby becomes nurse manager, and argues with Carter about her drinking. Luka flirts with a patient's mom and is caught emerging from a storage closet with her. Gallant has a rough day: Pratt butts in on a patient of his, and Stella Willis dies because Kayson didn't bother with thorough treatment.

Dr. Kovac's speeding causes a crash on an icy road. The ER staff treats angry elves and a female hockey player with a head injury.

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.

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.

Carter sticks up for Neela when the other attendings doubt her future in the ER. Neela caves to the pressure and accidentally gives a patient the wrong medication. Gallant takes the blame for her though. Sam and Luka try to plan Alex's birthday party. Frank visits on his way to therapy. Chen's home nurse quits after her dad behaves poorly.

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.

Neela is still struggling with her decision not to continue becoming a doctor. We discover that Ray is in a band. Kovac and Sam are amoureux, but where does that leave them?

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.

When a 16-year-old girl who had received a kidney transplant from her father arrives at the emergency room feeling dizzy, Carter traces the problem to a new drug that the girl was taking to control seizures related to her kidney dysfunction.

Neela (who's in Chicago) and Gallant (who's in Iraq) miss each other and write letters. Gallant also tries to save the life of a little girl.

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.

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.

Luka has a very bad day: New nurse manager Eve Peyton notices he doesn't want to work with Sam and tells him so. At the end of the day he's drunk and Abby takes him home.

Pratt's half-brother tries to get him to make ends meet with his estranged father. Clemente treats an infant chimpanzee and involves Abby and Neela on the secret case. Eve promotes Sam and her first tasks is to fire a beloved nurse.

Neela treats a religious teenage girl who turns out to be pregnant. Abby and Kovac struggle to figure out what to do with her unexpected pregnancy.

An unexpected visitor puts Clemente in the middle of a domestic dispute. Meanwhile, Luka and Abby await test results on their unborn child; Neela struggles with her surgical elective and Pratt ends up with an unexpected suitor when he participates in a charity bachelor auction.

Pratt gets to work in Darfur alongside Carter and his co-workers, but is troubled by astounding number of people needing care and finds himself making a dangerous journey.

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.

Weaver, Kovac, and the other doctors work frantically to try to save Jerry and a pregnant Abby, who were both critically injured during the shootout that left the ER in shambles. Meanwhile, Sam tries to escape from her ex-boyfriend and his criminal accomplices as they head north, but things quickly turn violent.

Gates is assigned to the case of a closeted gay man whose partner clashes with his family; Neela meets her new surgical chief, Dr. Crenshaw; and Pratt must cope with the flood of new interns.

A mysterious illness leaves little hope when a group of homeless kids enter the ER and one of them believes that Neela is a guardian angel in blue; Abby and Kovac clash over a possible case of domestic abuse; Pratt makes a shocking discovery about his brother, and Weaver is unexpectedly called into action when her television appearance becomes a real emergency.

It's Christmas in the ER. A homeless boy sends Gates and Ray on a mission. Meanwhile, in the ER, Neela oversees an unusual kidney transplant case; Sam takes a stand when a patient is dumped in an alley by another hospital; and Morris plays Santa for a special girl and learns the meaning of Christmas.

Kovac finds himself in a tense confrontation with Curtis Ames, and Abby must act to protect her family. Meanwhile, Neela and Gates rush to get Meg to the hospital while Sam's new home is soon under threat from fire.

What is suppose to be a departmental dinner organized by Kovac turns out to be the surprise of a lifetime for Abby when she soon learns it's a surprise wedding, secretly planned by the eager groom. Meanwhile, at the wedding, ER staffers enjoy themselves with music and booze while Neela finds herself the center of unexpected attention between Gates and Ray, which leads to a drunken fight and a shocking conclusion.

Season Finale: Luka postpones his honeymoon, leaving Abby, Joe and the ER behind to begin a different journey. Meanwhile, it's Moretti's first day as Chief of Emergency Medicine, and everyone feels the effects of his style, especially Pratt and Morris. Neela learns of Ray's fate, then joins an anti-war rally and finds herself in a dangerous situation. Gates faces a crisis on the home front.

Season Premiere. Moretti's first day is challenging as the ER is inundated with casualties from the peace rally - including Neela. Dubenko faces a crisis in surgery. Abby, Pratt and Morris conspire about how to deal with a shared problem. A new intern arrives unexpectedly, and Gates is reassigned.

Everyone at the ER is happily surprised to see Luka back from Croatia. Great news awaits Neela. Sarah once again needs rescuing by Tony, and patients are causing problems for Morris.

ER's 300th episode finds Luka and Abby hurriedly preparing to travel to Croatia after Luka's father passes away. Luka confronts Abby about the estrangement between them, and she eventually reaches out and asks for his help. A man rushes to the ER when his wife is seriously injured in a car accident, and finds someone very unexpected there with her. Julia holds a service to bless the ER and remember the patients that have been lost through the years.

Pratt and a new doctor on the scene disagree on how to teach the interns. Gates treats a young woman with serious heart problems. Abby heads to Croatia, and ponders whether and how to tell Luka about her unfortunate choices. Sam discovers that Julia has moved on in more ways than one.

When a drunk patient is admitted to the ER, his actions endanger everyone at County. Pratt is still pursuing his dreams of becoming Chief of the ER, and Gates is worried about his future with Sam. Luka unexpectedly runs into Dr. Moretti.

Abby's first day as an attending is bittersweet. Neela is hurt when she finds out Abby's news from someone else. Abby and the new ER Chief argue over how to treat a gunshot victim. Abby comes to Sam's aid when she faces a nurses' disciplinary board.

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.

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.

Carter finds himself struggling with County's new technology and procedures. After becoming frustrated with the in vitro-fertilization, Banfield and her husband discuss adoption as an option. Sam's mother arrives in an altered state of mind.

A camera crew shooting footage for a documentary interviews members of the ER staff. Detective Claudia Diaz is brought in, critically injured with gunshot wounds. Neela laments the lack of communication between her and Brenner. Sam struggles to reconcile with her mother. Carter's condition worsens quite suddenly.