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.

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.

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.

Dr. Weaver is in a difficult situation when an alderman tests positive for syphilis. Dr. Carter is impressed when he meets a man who runs an inner city clinic.

Dr. Weaver meets her birth mother, but their relationship changes when Kerry reveals she is gay. Dr. Carter causes a commotion when he confronts a couple hoping to scam some painkillers.

Kovac anxiously awaits the verdict between himself and Curtis Ames but fears the worst. Meanwhile, Neela disobeys her chief's orders and also questions her feelings for Gates, and Weaver unwittingly steals the spotlight from Morris in his big television debut.

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.

Carter finally works up enough nerve to ask Del Amico out. Jeanie tries to help Scotty decide whether to undergo an experimental treatment and Benton takes unexpected action during an operation with Morgenstern.

Sam and Luka go on the search for her runaway son, Alex. Meanwhile, Pratt and Lewis guide Abby, Neela and Ray, who have become R2's, on how to teach the new interns.

When Baby Joe is injured by a fall at the playground and rushed to the hospital, Abby is unable to reach Luka to tell him.

After another hospital shuts down, the ER is flooded with patients. Dr. Pratt resuscitates a heart-attack victim who had been pronounced dead.

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

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.

Kovac and Gates find themselves with a moral dilemma when a woman comes into the ER with acute liver failure; Neela finds herself questioning what is right when Manish decides to give up a kidney to a complete stranger. Meanwhile, Ray fights to get to the bottom of a cheerleaders accidental fall; Abby gets a prediction for her future; and Alex's troubles continue to intrude on Sam's work life.

It's time for changes at the ER when Anspaugh makes an unpopular decision. Abby has old demons to fight with, which distance her from friends and family. Even Luka seems to be at a loss to help Abby. Love is in the air when a secret romance blooms between two doctors.

Everyone in the ER is trying to cope with the loss of their colleague. The staff feels defensive toward the new Chief and her tough disposition. Gates and the new interns treat a bio terrorist who has a lethal secret that endangers them all. Neela makes a great effort to get Dubenko back on the surgery staff, and gets help from an unexpected source.

It's Halloween night, and the interns continue to be paired with the residents. Gates's teaching methods with Daria, and her responses, belittle Sam. A school fight results in a stabbing and a nose that won't stop bleeding, with Brenner treating the victims and being deeply affected by the truth behind their confrontation. The staff, especially Neela, are enthusiastic about a surprise visitor. Gates gets locked in a maintenance area with a quiet young boy.

Susan is forced into the role of parent when Chloe gives birth and both Chloe and her mother, Cookie, shirk responsibility. Doug is surprised and a bit frightened when Diane suggests they move in together. Unfortunately, Linda Farrell happens to be around to take advantage of his nervousness. Carter is offered the ER sub-I but turns it down in anticipation of receiving a surgical position. Peter receives unpleasant news; his mother has died.

Dr. Carter is allowed a cautious restart with small steps. An extremely blond Dr. Malucci is very curious who's made Dr. Chen pregnant. Dr. Benton has been written out of all the hospital's systems and is stunned by Dr. Romano. An unfortunate incident at a Science Fiction convention makes it look like scenes from the movie 'Mars Attacks'.

Dr. Carter celebrates Christmas at a clinic in the Congo dealing with low supplies and anti-Americanism, but in the meantime, falling for an AIDS worker named Makemba.

Carter returns to County General to hearty welcomes. Although Abby is shocked to learn that Carter's beautiful African girlfriend, Kem, is already pregnant with Carter's child, Abby has moved on with her life as well, going back to medical school.

A rape victim, barely able to speak, does all she can to help police find her attacker.

Abby has a dialysis patient in critical condition, but she cannot find his physician, who does not want to be bothered during the holidays.

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.

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.