On his return to Chicago, Carter gets a downright chilly reaction from Abby who asks him to return her apartment key. At work, they tip toe around one another, neither really willing to discuss their feelings. A new med student, Neela Rasgotra arrives for her ER rotation. Dr. Pratt is paying too much attention to her for Dr. Chen's taste. A woman passes out at the wheel of her car severely injuring herself and the three children in the car with her. Neela makes a good call in the case. Carter treats a man whose HIV has become full-blown AIDS. The ER itself is a bit chaotic due to major reconstruction. The ER desk receives a call from Africa saying that Luka Kovac has been killed. Carter decides to return to the Congo to retrieve his body.

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.

Luka Kovac arrives safely at County General and is hospitalized for treatment. His friend Gillian delivers John Carter's letter to Abby. Pretty much everyone gets to read it when Frank retrieves it from the garbage and passes it around. Greg Pratt has dinner with Chen and her parents. The dinner goes well but they have a serious argument afterward. Dr. Romano is unhappy with his prosthetic arm which makes him even more difficult to deal with. Some of the more senior nurses find their hours being reduced as a cost-saving measure and stage a walkout. Romano's response is to fire them all. Dr. Lewis treats a teenager with a serious heart problem but her parents insist that she not be told immediately. A new group of second year residents arrive.

Confident second-year resident Pratt wants to prove his abilities when he works the graveyard shift (11 p.m. to 7 a.m.), but his heroics sometimes backfire. Pratt shows contempt for a man, Ed Gamble, who presents no symptoms of disease but temporarily loses his speech. Chen continues to get in the way of Neela's progress as her jealousy regarding Chief Playa Pratt's flirtations with everyone who wears a skirt reaches new levels of ridiculousness.

Emmy nominee Bob Newhart guests as Ben Hollander, a distraught architect whose degenerating eyesight causes him to be 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.

Pratt and Kovac clash over a miscarriage-prone young woman who arrives to deliver a premature baby. Pratt wants to make heroic efforts to save the unborn child, while Kovac is adamantly against spending vast amounts of money to keep the forever sickly baby alive.

To everyone's amazement, Lewis makes a date to share a home-cooked dinner with the elderly Ben Hollander, her depressed patient who is going blind.

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

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.

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 from Africa full of surprises including a new love, Makemba ("Kem"). Pratt accidentally breaks a patient's neck while doing an unsupervised intubation. A whole nursing shift cannot go home until they find one missing Valium.

Abby and Neela are assigned to a month-long rotation in the neonatal intensive care unit where they experience emotional roller coasters while caring for the sick infants.

Dr. Carter's girlfriend makes an impression as she observes ER operations. Dr. Gallant is almost shot during a domestic incident. Dr. Weaver dedicates a center to the memory of Dr. Romano.

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.

Carter misses his pregnant girlfriend who has returned to Africa. A family of four is rushed to the emergency room after suffering carbon monoxide poisoning from their faulty furnace--forcing the claustrophobic Neela to accompany a newborn baby into an extremely uncomfortable hyperbaric chamber.

Dr Morris agitates a patient who then leaves, steals a tank, and rampages through Chicago on his way to County General. He makes it all the way to the ambulance bay before the CPD finally stops him. Sam tries to figure out her relationship with Kovac while Gillian shows up at the ER to cement plans for dinner with Carter, Kem and Kovac - making things that much more difficult. Neela confronts Frank about his arrogant bigotry, bluntly telling him she wants nothing from him but silence from this point forward. During the initial onrush of patients due to the tank rampage, Frank has a heart attack which is, thankfully, caught. Frank's wife and daughter show up and are rushed up to the cath lab where Dr. Pratt is helping Dr. Kayson keep Frank alive. In the end, Neela winds up in the family room with Frank's family listening to them describe a side of Frank that no one has ever seen. Meanwhile Kovac treats a 13 year old with chlamydia and counsels him to contact his sexual partner - which turns out to be quite a few teenage girls.

Carter defends his protégé Neela when Weaver and other doctors rate the residents. Carter urges his student to be more proactive in the emergency room, but Neela goes too far in treating a patient with a brain injury--and sympathetic Gallant errs further by falsifying a medical report. Meanwhile, Chuck protects pregnant Lewis from a pervert who is harassing her. Kovac treats a disoriented young boy whose dad fears that tests will reveal he is not the boy's biological father. Chen is unable to find a caretaker for her combative father. And Corday is uneasy about dating two men at once.

Weaver rushes to the aid of her wife, Sandy Lopez, when the firefighter is severely injured while working and must now battle for her life. Frightened Weaver whispers hope to Sandy by reminding the victim of their newborn child.

Pratt struggles to diagnose a woman who suffers mysterious chronic seizures. An attractive woman, Campbell, informally accuses flirtatious Pratt of sexual harassment. Abby ponders how to get her contentious patients' attention during her psychiatric department rotation.

Carter greets the returning Kem, but their meeting with his father, Jack, gets tense after Carter announces plans for his grandmother's estate.

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

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.