A frazzled Dr. Carter returns from his harrowing mission to the Congo only to be confronted by a hostile Abby while an exotic new British medical student causes a stir when she unexpectedly helps a patient -- and angers Dr. Chen as Dr. Pratt flirts with her. In addition: a concerned Dr. Pratt works the margins to help an HIV-infected patient obtain the necessary medical insurance; a woman and her young children are treated after their wrecked car is struck again by a large truck; construction workers add to the chaos of the emergency room; Dr. Romano sports a new look -- and Carter gets an ominous call from Africa.

Dr. Carter returns to the Congo to search for the body of a fellow doctor and reunites with several associates but the chaos, stench and danger of the country’s long civil war threaten to curtail his efforts -- and again put him in harm’s way. Elsewhere in the strife-torn country, Dr. Kovac is seen in flashbacks as he battles debilitating malaria while he ministers to the sick and dying in a land where life is cheap at best.

Abby’s frustrating day gets worse when she gets a special Dear John letter from Dr. Carter in the Congo while her fellow nurses threaten a walkout and her opinions are ignored -- especially when she is chastised as she seeks to inform a teenaged girl, with failing lungs and heart, that her life is in grave danger. Elsewhere, Dr. Romano’s mood gets nastier when he is fitted with an antiquated hook for his missing arm and he takes out his rage by firing several much-needed nurses. In addition, three new second-year residents join the staff -- including the self-assured Dr. Coop. Dr. Pratt uneasily meets Dr. Chen’s old-fashioned parents for dinner, and the playful Dr. Dorset makes an impression with his style and substantial skills.

A confident second-year resident Dr. Pratt wants to show off during the graveyard shift but his heroics sometimes backfire, especially in his contempt for an asymptomatic husband who temporarily loses his speech -- and in the case of a boy whose treatment is delayed after he swallows a quarter. As Dr. Weaver decries the incompetence of her staff, she too makes a grievous error while a screaming man with a broken leg must wait endless hours and Neela deals with a little girl who arrives with her beloved grandmother whose status is DNR -- Do Not Resuscitate. Elsewhere, Abby finds herself desperate for money and credit and later meets both Dr. Kovac and his new girlfriend. Likewise, Dr. Corday warms up to Dr. Dorset.

Dr. Lewis fears for a distraught architect whose degenerating eyesight makes him despondent while a spirited new nurse replaces Abby -- who decides to return to medical school. Elsewhere: disaster strikes when the doctors suspect a mother is abusing her child; Dr. Corday learns something shocking about the charismatic Dr. Dorset, and a green medical student is overwhelmed by the chaos and grisly conditions of life in the E.R.

Drs. 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 tiny soul while Kovac is dead-set against spending vast amounts of money to keep the child alive, but forever sickly. Elsewhere, Dr. Lewis enjoys her time with a sarcastic patient who once threatened to take his own life over his impending blindness. A distracted Kovac also runs afoul of a psychiatrist who over-medicates an abused foster child who wants to go back to his drug-addled mother. Plus, a chatty, upbeat pharmaceutical rep makes the rounds offering goodies, a man gets violent over an exorbitant bill and Dr. Coop makes a romantic play for Dr. Chen.

A busy Dr. Lewis plans a home-cooked dinner with the elderly Hollander -- her depressed patient who is going blind -- treats a stressed-out housewife, arranges for an IRS audit, and then hides the detached arm of the nasty Dr. Romano. Elsewhere, Neela and Dr. Pratt treat a vulnerable 18-year-old who was attacked in jail and Dr. Gallant must gamble with a risky hospital transfer to help a young septic cancer patient. Meanwhile, Dr. Kovac clashes with Dr. Corday over the treatment of a patient she suspects needs an appendectomy and nurse Sam parks her precocious son in the E.R. for a day where the kid gets an eyeful.

On Thanksgiving, the staff struggles with a shortage of doctors as Abby treats an HIV-positive woman who thinks she might be pregnant while suffering from severe bleeding and an unexpected helicopter crash on the hospital rooftop threatens to harm everyone in the hospital. Nearby, Dr. Lewis is unaware that her ex-husband Chuck was involved in the disaster. Elsewhere, Dr. Romano threatens to file a serious complaint against the brash Dr. Pratt and Romano continues to ride medical student-nurse Abby with tough medical questions -- even as she wonders about what Dr. Carter might be doing that same day in Africa.

Two distinct cultures collide when Neela treats two Amish teenagers involved in a car accident who are exploring the outside world to determine if they want to return to the reclusive society while Dr. Corday and a few others mourn the loss of a talented colleague. Elsewhere, Sam clashes with sympathetic Dr. Kovac when he pays too much attention to her trouble-prone teenaged son Alex while Dr. Lewis is pained when an unconscious 5-year-old girl cannot be traced to any parent or guardian. In addition, Dr. Pratt scopes out the beautiful Valerie who is visiting her nervous brother Dr. Gallant.

On Christmas Eve, a chilled emergency room staff do their best to observe the holiday while a crusading Dr. Carter does the same half a world away in a run-down Congolese medical clinic as recent flashbacks reveal his clashes with Makemba, a beautiful native AIDS worker over the meager resources -- and they slowly fall in love. As Carter re-adjusts to the heat, filth and dangers of the region, he keeps in touch with his Chicago friends and embarks on a personal mission to save a pregnant mother who is dying of AIDS, he is confronted by anti-Americanism from his French comrades. Even so, Carter is determined to bring the joy and love of Christmas to the local children of Kisingani.

The return of Dr. Carter from Africa prompts various reactions, especially when he is accompanied by his new love Makemba -- and Carter has other surprises in store -- while Dr. Pratt squares off against Dr. Gallant over a personal matter. A busy Pratt also finds time to treat a young victim of a car accident whose case is complicated by a rare form of osteoporosis and takes an interest in an elderly woman suffering from dementia who believes he is her son. In addition, a whole nursing shift cannot go home until they find one missing valium pill. Elsewhere, Dr. Kovac informs Dr. Weaver about his departure date and Carter deals with a malnourished woman and her equally famished family.

A reluctant Abby and Neela are assigned to the dreaded NICU -- the Neo-natal Intensive Care Unit -- a separate floor where they are confronted with a whole new universe of jargon and helpless babies fighting for their lives as anxious parents wait for miracles that often don’t come. The wrenching marathon is part of their month-long rotation, and the pair begin to confront their own fears as they are tested emotionally and professionally. Eventually, they begin to bond with the Chinese parents of sick twins, a baby boy with a faulty heart, a praying mother who refuses to give up hope for her comatose infant -- and even Dr. Weaver, whose newborn baby with Lopez needs the NICU’s help.

Dr. Carter makes the mistake of bringing his wide-eyed girlfriend Kem to observe the emergency room where she makes an impact -- wanted or not -- almost everywhere she wanders, ranging from an AIDS ward to the classroom and even in an unsanctioned ridealong with the paramedics. The complex Dr. Pratt has a hard night and questions his abilities as he treats a variety of patients, including a young sledder who breaks his back in the snow and a elderly man with fluid in his lung. Meanwhile, Dr. Gallant accompanies the paramedics and is almost shot in a violent domestic dispute where he befriends a frightened boy, and Dr. Weaver dedicates a new center to Dr. Romano’s memory that has everyone buzzing.

Life and death assume an even higher profile as single-mother Sam treats an abused and newly pregnant teen as well as a wife who sees her injured family melt away after a car accident -- while Dr. Carter takes a holiday to show Kem the wonders of a wintry Chicago. Elsewhere, a risk-assessment expert is hired to observe the E.R. and is shocked at the abounding mayhem -- especially when Sam roughs up a patient’s friend. Abby and Dr. Pratt restrain an undocumented man who wants to check out despite testing positive for tuberculosis while Sam is quizzed by her son Alex about her interest in Dr. Kovac.

While Dr. Carter pines over his separation from his pregnant girlfriend in Africa, a family of four is rushed to the E.R. after suffering carbon monoxide poisoning from their furnace -- forcing a claustrophobic Neela to accompany a newborn baby into an extremely uncomfortable hyperbaric chamber to extend its life. Elsewhere, Dr. Lewis is upbeat about her future with Chuck while Nurse Sam has reason to ponder her relationship with Dr. Kovac. In addition, Lewis and Abby treat a maniacal man who’s rushed in covered in blood, while Dr. Weaver counsels a mother whose young son tests positive for leukemia. Amid the chaos, Dr. Chen returns from China with her sick father in tow.

A psychotic patient makes good on his promise to punish the medicos when he steals an Army tank and grinds his way across Chicago towards the hospital while Sam grows jealous of Dr. Kovac’s visiting French friend Gillian -- and one of the E.R. staffers suffers a heart attack. Elsewhere, Kovac is startled at the lack of concern among some 13-year-olds who are diagnosed with chylamidia; Sam ponders the curious relationship between a concerned teenaged girl and her sick father who is in full cardiac arrest, and Dr. Corday is enchanted with a charming fellow surgeon.

When Dr. Weaver and other attending doctors rate the residents, Dr. Carter feels obliged to defend the potential of his protegee Neela, but when he urges her to be more pro-active in the E.R., she goes too far in treating a brain-injury patient -- and a sympathetic Dr. Gallant errs further by falsifying a medical report. Elsewhere, a pregnant Dr. Lewis is harassed by a sexual pervert which prompts Chuck to defend her, while Dr. Kovac treats the disoriented young son of a man who fears that tests will reveal he’s not the boy’s father. In addition, Dr. Chen is at wit’s end over finding a caretaker for her combative father and Dr. Corday is uneasy about dating two men.

Dr. Weaver rushes to the aid of her female partner Sandy Lopez when the firefighter is severely injured on the job and must fight for her life -- as a frightened Weaver offers whispered hope by reminding the victim of their newborn child. A pregnant Dr. Lewis suffers labor pains and is confined to bed rest, while tension remains between Dr. Gallant and Neela as an investigation begins into the suspicious death. In addition, Dr. Corday gets a pleasant surprise. Neela and Abby get the news about their board scores and Dr. Chen and Pratt treat a frustrated senior citizen who does not want to burden his family with his care.

Dr. Pratt’s reputation as a flirt catches up to him when an attractive woman informally accuses the young doctor of sexual harassment while Pratt also struggles to diagnose a woman who suffers mysterious chronic seizures. Meanwhile, Abby ponders how to get the attention of her contentious patients during her psych rotation and Neela finds herself studying strokes in a lab populated by brainy but bizarre graduate students. Elsewhere, Sam tries to resist the appeal of the reformed father of her son when he temporarily moves into her apartment -- giving a concerned Kovac something to think about. In addition, Dr. Weaver vows to fight for her baby son and Dr. Chen is at wit’s end when she brings her combative and ailing father home.

A panic-stricken Dr. Weaver faces a life-defining moment when she is ordered to give up her son to the Lopez family while Dr. Carter greets a returning Kem -- but their meeting with his father is tense after Carter announces plans for his grandmother’s estate. Elsewhere, Abby is in the midst of her psychiatric rotation and tries to help a seizure-prone mother with a controversial drug treatment. Meanwhile, Neela impresses everyone with her lab research, especially when she helps one of the reckless students after he experiments on himself. In addition, Dr. Kovac’s relationship with Sam and her son Alex grows awkward when Alex’ father returns.

Dr. Carter is alarmed as he rushes his pregnant girlfriend Makemba into the E.R. when he suspects trouble, while Dr. Corday gets a jolt from the past when the late Dr. Greene’s teen daughter Rachel shows up with her boyfriend looking for a haven -- and some morning-after pills. Elsewhere, Neela prepares for her graduation by welcoming 20 family members while Abby -- who hasn’t passed the boards yet -- prefers to sit it out. Before the ceremonies, Neela and Dr. Pratt seek out an overweight teenager whose blood pressure could indicate deadly heart disease. In addition, Nurse Sam is uneasy about her ex Steve moving back in her apartment while Frank loudly returns after his cardiac attack.

Dr. Kovac plays the Good Samaritan when he stops to help a stranded female motorist and her young son until they are struck and gravely injured by a car -- forcing the doctor to use all of his skills to keep them alive until specialists can operate at the hospital. Elsewhere, Abby waits for her board results and treats an ornery curmudgeon who feels he’s been forgotten by the hundreds of students he taught as a schoolteacher. Meanwhile: a pensive Neela heads for the University of Michigan to begin her internship; her fellow doctors question the bruises on Dr. Chen’s face; Dr. Pratt keeps a mentoring eye on a young heart patient but remains disdainful towards a gangbanger patient patient; Dr. Weaver hopes to gain custody of her son, and Sam takes action when it appears that Steve is back for good -- and up to no good in influencing their impressionable son.