When an ambulance explodes, Abby wakes up and realizes that she has been injured. In a selfless act, she rushes to check on the others in the ambulance. A mother and daughter are also brought in due to the explosion, and Abby misdiagnoses the case. Meanwhile, Morris and Neela struggle to keep up with the injuries sustained from the explosion.
Banfield's attitude causes the whole ER staff to feel defensive. Gates and the new interns attempt to save the life of a terrorist while risking their own. Neela finds an advocate in her fight to get Dr. Dubenko back on the surgery staff.
Neela finds out Abby's good news second hand. Catherine Banfield and Abby butt heads on how to treat the victim of a gun shot wound, that has just been admitted into the ER. Finally, Abby comes to Sam's defense before a nurses' disciplinary board.
When Banfield runs out to get a cup of coffee, she's caught off guard by a man trying to steal her wallet. Dr. Dubenko is back on the surgery team thanks to Dr. Brenner, and a young gymnast arrives at the ER after a fall, but Banfield and Gates think a family member may have caused the injuries. Meanwhile, Gates gets upset when he finds out that Sarah got her tongue pierced.
Gates feels neglected because Sam is distracted while studying for her pharmacology exam. A stab wound victim comes into the ER after a school fight and Brenner tries to get to the bottom of the story. Morris surprises Neela with an unexpected visit from Ray Barnett. Meanwhile, it's Halloween and Gates gets locked in a stairwell with a quiet, young boy.
Morris takes Chaz under his wing and teaches him some sensitive medical procedures much to the disappointment of Dr. Banfield. Neela gets angry when Dr. Banfield challenges her authority with one of the interns. Meanwhile, Gates goes over the line with Sam.
When Banfield takes a run, she finds herself trying to rescue a three-year-old girl from drowning. Meanwhile, Gates tries to pull some strings to help a homeless war hero and friend. Later, the interns continue with their struggle to keep up in the fast-paced ER.
Sam becomes frustrated with Gates when he obsesses over finding a homeless war hero. Neela is mad at an intern after he gets the surgery department into a lawsuit. Finally, a husband and wife come to the ER after someone tries to burn down their house.
Neela testifies in court after treating a patient that eventually died. Alex and Sarah go to a party against Sam's will and get into a bad car accident. Meanwhile, Morris and Banfield are snowed in at an ER conference in Nebraska.
Morris receives an unwanted package from his father at the ER doorstep. Sam is anxious about getting Alex off of the ventilator after his accident. Meanwhile, a pregnant woman with a high-risk pregnancy is in danger of getting deported.
Banfield treats two brothers, both injured during a drug deal gone bad. Gates is mad at Sam, so she doesn't tell him that Alex is coming home from the hospital. Neela thinks about pediatric surgery after helping a young girl with sickle cell anemia. Meanwhile, Dr. Banfield and her husband make an important decision about the future.
Neela keeps having recurring dreams about her crazy day trying to save a young girl with sickle cell. Gates tries to save a patient that jumped out of a window after walking in his sleep. Meanwhile, Neela is surprised to see Dr. Corday, after she goes in for an attending interview.
Morris treats a young girl that was hit by a car while riding her bike. Meanwhile, Gates still has feelings for Sam, and Neela deals with Dr. Brenner's return from Australia.
Gates and Morris treat an older man that comes into the ER after being assaulted. Meanwhile, Dr. Brenner discovers a shocking diagnosis on another patient while treating a mother with late stage cancer. Later, Sam gets a visit from her sister. Meanwhile, Dr. Morgenstern decides to visit County General when he hears a mentor is gravely ill.
There is a car accident in the ambulance bay leaving one woman badly injured and in need of hip surgery. Brenner searches for a family member willing to look after the daughter of the injured woman. Meanwhile, Morris deals with an insurance company's unwillingness to pay for an MRI for a 78 year-old-man. Finally, Neela informs Brenner of her offer in North Carolina.
Valentine's Day in the ER brings Neela and Dr. Brenner closer. Gates treats a mushroom hunter who has breathing problems, on his wedding day. Banfield refuses to give up on trying to get pregnant and Neela gives a little girl great news about her mother, but the mother's condition worsens when a mistake is made. Meanwhile, Dr. Carter returns to the ER.
After getting frustrated with in vitro fertilization, Dr. Banfield and her husband decide to try an adoption agency to fulfill their dreams of having a family. Dr. Carter quickly tries to jump back into working at County, but struggles with all the new procedures and technology. Sam is shocked when her mom comes into the ER in an altered state of mind.
A camera crew interviews the staff at County General for a documentary on emergency medicine. Morris' cop girlfriend gets injured on the job and is rushed into the ER with gunshot wounds. Neela wonders why her relationship with Brenner lacks communication. Sam struggles to make amends with her mother.
Neela and Sam are shocked when they arrive back at the airport with transplant organs only to find that their plane has left them. Dr. Carter gets a surprise visit from an old friend while waiting for his kidney transplant. Dr. Banfield bonds with an abandoned baby boy that is left at the ER.
It's Neela's last day and everyone in the ER seems to have forgotten that she is leaving. Neela proves she is ready to be an attending when she and Dr. Dubenko argue about the treatment of two surgical cases. Meanwhile, Brenner has an epiphany about his troubled past.
Many of the ER doctors and nurses help out at Camp Del Corazon, a camp for kids who have had open heart surgery. Working alongside the camp counselor, Morris and Brenner make a huge impact on several kids at the camp. Meanwhile, Dr. Banfield and her husband feel their adoption dreams slipping away when a young mother comes back for the child she abandoned in the ER.
Gates works on a young teen brought in with alcohol poisoning after playing a deadly drinking game with friends. Dr. Carter opens a new medical facility for the underprivileged in Chicago and some old friends from County General all come to show their support. It's Sam's birthday and Alex and Gates surprise her with a special gift. Meanwhile, Carter works with an intern to save a mother in labor with twins.