Carter returns from Africa to find Abby giving him a cold shoulder. A new med student arrives at the ER from Britain even as the ER itself receives a face lift.
Carter fights against the dangers of the Congo to try and secure the body of his friend and colleague Kovac. As Carter works towards his goal in the present, we learn what happened to Kovac in his absence. Carter eventually learns that Kovac actually survived because the fighters believed that he was a priest and spared his life.
Abby has an awful day compounded by her reading of a letter that Carter sent back from the Congo. Romano takes out his anger on the staff and shorts them a few nurses. Pratt meets with Chen's parents.
A graveyard shift seems to Pratt to be the perfect grounds to prove his competence, but he stumbles. Weaver questions her staffs ability, only to have her own questioned. Abby has to deal with money troubles and meeting Kovac's new girlfriend.
Lewis handles an aging architect with failing eyesight. Abby decides to continue her education and is replaced on staff by a new nurse. A young medical student is thrown off by the reality of the ER.
Kovac and Pratt butt heads over how to deal with a premature baby's birth. Lewis and a patient going blind spend time together. Coop tries to land Chen. A pharmaceutical rep named Terra goes through the ER.
Lewis has a busy day between her personal and professional commitments as she prepares to entertain Hollander. Kovac and Corday butt heads over a patient's treatment. Sam's son visits the ER for a day. Neela and Pratt try to help a teen that was beaten in prison.
The ER is swamped on Thanksgiving and the doctor shortage doesn't help the staff handle things. To compound matters, a helicopter crash causes destruction all around the ER and Romano is caught at ground zero.
Neela helps two Amish teenagers who were injured while exploring the modern world. Romano is mourned. Kovac's kind treatment of Sam's son raises her ire. Lewis tries to track down the parents of an injured young girl. Pratt checks out Gallant's visiting sister.
Christmas Eve is celebrated by both the doctors in the ER and Carter in a Congolese clinic. Carter falls for his co-worker Makemba and tries to bring the holiday to his patients.
Carter returns from Africa with Makemba on his hand. The nurses search the hospital for a missing valium. Kovac informs Weaver of his upcoming departure.
Abby and Neela receive the Neo-Natal Intensive Care Unit assignment for their rotation and are put through a trial of fire even as Weaver's baby is in need of the NICU.
Carter's girlfriend has a wide-ranging impact on all aspects of the ER during her visit. Pratt feels unsure of his aptitude as a doctor. Gallant nearly takes a bullet when he rides along with paramedics. Weaver dedicates a center to the deceased Dr. Romano.
Sam balances her time between a newly pregnant teen and a family broken in a car accident. Carter escorts Kem around Chicago. The ER comes under the watchful gaze of a risk-assessor.
Neela fights off her fear of enclosed spaces to help a newborn suffering from poison inhalation into a hyperbaric chamber. Carter pines for his girlfriend. A man arrives in the ER covered in blood. Chen comes back to the ER from China.
An imbalanced patient offended by Morris takes his hatred out on the city and the ER with a tank. Sam is envious of Kovac's visiting lady friend. A surgeon makes in-roads with Corday. Frank suffers a heart attack and has to have emergency bypass surgery.
Carter's push for Neela to make her own choices in the ER ends in tragedy and Gallant tries to lend a helping hand by falsifying the medical report. Chuck tries to protect Lewis from a pervert and his punch sends the man to the ER. A man worries that Kovac's test on his child will show that he is not the real father. Corday feels pressured from her active love life. Chen searches for proper care for her father.
Sandy arrives at the ER as a patient when her job as a firefighter puts her at death's door. Lewis's pregnancy keeps her in bed. Gallant and Neela start to have to field inquiries into the death of a patient.
Pratt is accused of sexual harassment. Abby has a hard time with patients on her psych rotation as Neela studies strokes. Kovac worries as Sam's ex, the father of her child, moves in with her. Weaver fights for her son and Chen fights her father.
Weaver is told to turn over her son. Carter decides what to do with the family fortune after his father meets Kem. Abby tries to help a mother who goes into seizures frequently. Neela shows her worth in a lab study. The relationship between Kovac and Sam comes under strain when her son's father returns into her life.
Carter worries about Kem's pregnancy as he takes her into the ER. Corday gets an unexpected visitor in the form of Rachel Greene. Abby sits out graduation even as Neela welcomes a big group of family. Frank comes back from his heart attack.
Kovac saves the lives of a woman and her son at the scene of a car accident. Abby learns the results of her test have been waiting for her all along and tries to help a retired teacher see the point to his life. Samantha tries to escape with her son. Neela finds her new location to be a poor fit.