Much to Ray's dislike, a surrogate mother in labor doesn't want to have a C-section and endangers the life of the baby. Meanwhile, Sam tells Luka she and Alex are moving out. Pratt meets his half-brother and -sister, and Abby makes a difficult decision about a young boy.
The rainy night brings in diverse patients, including a mother involved in a car accident with her baby, a man with a satisfaction facilitator, and a comatose patient who suddenly wakes up. Also, Sam stands up to Eve and her strict ways and Jerry gets struck by lightning.
A new attending, Dr. Victor Clemente, comes aboard and quickly makes a stir in the ER. Abby's breast cancer patient convinces her to take a long awaited test. Luka befriends a young woman who awakes from a six-year coma. Also, Weaver shows Clemente who runs the ER.
Pratt's half-brother tries to get him to make amends with his estranged father. Clemente treats an infant chimpanzee and involves Abby and Neela on the secret case. Eve promotes Sam and her first tasks is to fire a beloved nurse.
Gallant impulsively asks Neela to marry him that exact day; she says I do but soon gets cold feet. Morris stands up to Weaver on a patient's course of treatment. Luka, Sam and Clemente treat a boy who contracted HIV from his mother. Also, Abby and Luka redefine their relationship and Luka is named the new Chief of Emergency Medicine.
Pratt and Weaver try to create a Christmas miracle when they work to save a girl wounded from gunfire. Eve gets into trouble after punching a disruptive patient. Also, Abby has a special gift for Luka.
Ray helps an old friend escape from her abusive father. Dubenko volunteers in the ER but can't seem to handle a slow day. Abby and Kovac go baby shopping, while Neela gets unexpected and upsetting news from Gallant.
Dr. Nate Lennox, a former professor with ALS, is brought in as the progression of his disease is chronicled through his own flashbacks as he is treated by each of the doctors at one point. As Lennox wants to give up, Abby fights to convince him to keep on fighting.
An unexpected visitor puts Clemente in the middle of a domestic dispute. Meanwhile, Luka and Abby await test results on their unborn child; Neela struggles with her surgical elective and Pratt ends up with an unexpected suitor when he participates in a charity bachelor auction.
In Sudan, Carter and a colleague struggle to save a woman who was raped by a band of militants. Back in the ER, Clemente asks to return to work after the shooting incident, but Kovac refuses. Meanwhile, Neela and Pratt have a work dispute, and, in a related incident, K.J.'s father shows up again in the ER.
Weaver contemplates hip replacement surgery after she finds it hard to do her labor-intensive job. Meanwhile, Kovac tries to ease Abby's fears about raising a child together. Neela decides to attend a support group for military spouses but when she offers her opinions on the war, the meeting turns into a debate. And after Sam treats a fainting victim, she finds herself with an intriguing job offer.
Abby and Luka desperately try to keep a young woman brought into the ER with stab wounds to the neck alive. As her condition begins to worsen, Clemente steps in and tries a risky procedure on the girl in order to save her life. Meanwhile, Neela pulls an all-nighter in preparation for a speech at a surgeon's convention, Ray treats a man claiming to have swallowed a bottle of pills, and Sam decides to take a part-time job with Richard to help her with childcare expenses.
When two teens are in a car accident, Abby and Morris struggle to figure out what is wrong with the unconscious girl. Meanwhile, Neela gets a visit from her in-laws and discovers some troubling news. Kovac tells Abby that he plans to go to Africa and help Carter, but when he realizes Abby is not crazy about the idea, he decides to send someone else in his place. Sam starts her new job with Elliot and quickly starts to love the the perks.
Dr. Clemente's paranoia spirals out of control after he receives threatening mail from his girlfriend's husband. Abby senses something not right when a grandmother and granddaughter are brought into the ER. Sam's jailed ex-husband Steve is brought into the ER and everyone but Neela assumes he is faking sick. Meanwhile, tensions grow when Morris and Albright argue over a patient, Pratt heads to Africa to help Carter and quickly realizes how difficult life will be; Weaver finishes physical therapy.
Chaos reigns in the ER when two prisoners are brought in for treatment, but instead plot a violent escape. Their desperate actions place one doctor in harm's way, and forces one nurse to become a tool in their plan.