Carol goes into labor on the L. With the help of Luka, she makes it into the ER and delivers one twin, Tess, there. She is then moved to the OB and put in the care of OB nurse Abby Lockhart. Dr. Coburn delivers Kate through an emergency c-section but Carol and both babies turn out to be fine. When Mark has to leave Thanksgiving at her house to be Carol's Lamaze coach, Corday is stuck with his father and Rachel. Dr. Dave helps Carter with a diagnosis of a very rare disease.

The episode was rated 7,98 from 95 votes.

Abby awakens after the ambulance explosion and rushes to check on Pratt; Sam and Gates rush to the scene; Morris and Neela struggle to keep up with Pratt's injuries.

The episode was rated 7,99 from 74 votes.

Greene misdiagnoses a pregnant patient, leading to a long and arduous surgery.

The episode was rated 8,00 from 156 votes.

Kerry investigates Synergix, an ER management group specializing in balancing budgets. She is later forced to fire Jeanie. In turn, Jeanie is asked by Al to move to Atlanta with him. Greene is still suffering from the aftereffects of his attack, snapping at patients and staff alike. Dr. Ross is stunned by a collect phone call from California informing him of his father's death. Benton clashes with Corday after she apparently "steals" a rare procedure out from under his nose. Carol meets with Carter's grandmother to pitch her idea for a free health clinic. Anna is perturbed when she discovers Carter's wealthy background.

The episode was rated 8,01 from 114 votes.

Benton struggles with the idea of taking a DNA test to determine whether or not Reese is actually his son. As the signs continue to pile up, Kerry and Mark use a fake patient to convince Dr. Lawrence of his Alzheimer's. Carter has trouble persuading a woman from a nursing home fire to sign a DNR for her husband and later is asked to forge charts for a family with no insurance. Carol continues to meddle in Meg's life, having her arrested so that she can be detoxed. Cleo is blamed for an explosion in the suture room, but it may actually be Dr. Dave's fault.

The episode was rated 8,02 from 95 votes.

Carol is held hostage in a bungled convenience store robbery. Her medical skills are put to their toughest test as she works feverishly to save the gravely wounded store owner.

The episode was rated 8,03 from 128 votes.

Carol resuscitates a terminal cancer DNR to say goodbye to her family, and realizes that life is too short. She runs out of the hospital after saying a quick goodbye to Luka and Mark and hops on a plane to Seattle to see Doug. Carter's mental status is dissipating rapidly to the point where he almost kills a woman. Chen notices and tells Mark her concern that Carter is bipolar. Weaver goes on the warpath after noticing ER staff taking shortcuts in their work, including Abby, who discharges a woman prematurely without running extra tests. Corday offers Malucci a sobering assessment of his performance. Mark prepares to bury his father and enjoys his daughter's company.

The episode was rated 8,04 from 113 votes.

Dr. Nate Lennox, a former professor and mentor of Abby's, is brought into the ER in the last stages of ALS disease. In a series of flashbacks at County, the progression of his illness over the last six years is shown. He wants to give up, but Abby is determined to give him the strength to keep fighting.

The episode was rated 8,05 from 65 votes.

The staff springs into action when Dr. Greene is violently beaten by an unknown assailant. Dr. Ross treats the son of a wealthy man, leading Carol to suspect Doug of giving the child special treatment. Greg demands that Jeanie choose between him and Al. Speculation runs rampant when a torrid novella, author unknown, is found at the admit desk. A new pediatrician arrives from Philadelphia. Olbes shows up out of uniform for a change, bringing in her grandfather, who has suffered a stroke. Carla is admitted to the hospital after she goes into premature labor; the contractions are stopped for now.

The episode was rated 8,05 from 119 votes.

Mark finds himself manning a very crowded ER on his scheduled night off, filling in while Doug is out with whiplash and Susan meets with her lawyer. He tries to juggle hunger pangs, 40+ patients in the waiting room and a never-ending stream of traumas.

The episode was rated 8,07 from 132 votes.

Greene and Weaver threaten Doug over his illegal treatment of Josh McLean. Dr. Rosher ingratiates himself with Anspaugh. Corday receives a letter from Romano informing her that he won't be sponsoring her for another year. A despondent patient shocks Carol with an unusually violent act. Kerry becomes upset when Anspaugh tells her that even though she has been Acting Chief of Emergency Medicine for a year, the hospital still plans a nationwide search for a permanent one. Carter accuses Max of taking some Percocet from a medicine cabinet. Benton arranges a hearing test after a day care worker tells him that Reese is unresponsive.

The episode was rated 8,08 from 106 votes.

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.

The episode was rated 8,10 from 80 votes.

The ER must be evacuated when several workers at a chemical plant track benzine all over the floors. After Weaver is felled by the poison, Carter takes over, directing the evacuation. Dr. Corday does a ride-along with EMTs and rescues a man trapped under a building. Doug and Carol are trapped in the elevator with a sick child.

The episode was rated 8,12 from 125 votes.

Weaver discovers Carter and Lucy. As police begin to arrive, Benton rushes between the two, being the only surgical resident on duty. Greene and Corday are paged to return to the hospital. Carter almost loses his kidney, but with quick thinking by Anspaugh, Benton is able to save it and Carter will be okay. On the other hand, Lucy has her chest cracked because her heart stops but she is stabilized. In the OR waiting room, while waiting for emergency surgery to fix a life-threatening blood clot, Lucy flatlines. Romano and Corday desperately try to save her life but she dies and the staff receives the news. Meanwhile, Paul Sobriki is found running naked down Michigan Avenue and is brought in. His wife arrives at the ER; incapable of believing her husband would be capable of such a violent act. And while Benton is busy with Carter, Cleo is forced to crack a man's chest open to save his life, resulting in Benton's ire.

The episode was rated 8,19 from 126 votes.

Mark decides to use his remaining time to help "fix" Rachel and takes her to Hawaii to show her where he grew up. He teaches her how to surf, and how to drive a stick shift. Mark catches her chasing one of his Vicodin with a shot of vodka and confronts her about wasting her life. One day after surfing, he has a seizure, and Elizabeth arrives with Ella in tow. She wants to take him home, but he refuses. Early in the morning, he dies. After the funeral, Rachel tells Elizabeth she'd like to visit Ella, and Elizabeth agrees.

The episode was rated 8,21 from 119 votes.