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.

The ER prepares to take in victims from a plane collision, while Neela and Pratt head out to the crash site where Neela makes heroic efforts. At the end of the day, Neela gets a surprising visit.

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.

Pratt struggles to get a straight story when two abused boys come into the ER with their father. Two U.S. Army officers enter the ER.

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 steps up to Eve and her strict ways and Jerry gets struck by lightening!

A kidnaped girl is the victim of police shooting. Abby is stuck in the middle of a disagreement between Luka and Clemente. Neela receives a phone call from Iraq. Later, Luka and Abby share a kiss.

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.

A new attending, Dr. Victor Clemente, comes aboard and quickly makes a stir on 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.

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.

Pratt departs for Africa with attitude to spare but makes his first contact with harsh reality before the plane lands. Abby senses something is not what is seems when she treats a 12-year-old and her grandmother, then differs with Luka over the best course of action. A prisoner is brought to the ER with what everyone thinks is a fake case of appendicitis. Morris is dressed, and ready, to impress, but Albright’s not. It’s time for Kerry to return to work and Clemente doesn’t know when it’s time to leave.

Pratt gets to work in Darfur alongside Carter and his co-workers, but is troubled by astounding number of people needing care and finds himself making a dangerous journey.

Gallant impulsively asks Neela to marry her that exact day, she says I do but soon gets cold feet. Morris stands up to Weaver on a patients 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.

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.

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 Luka answers a call for help, he discovers not everyone is pleased. Will he honor his commitment, or ask a colleague to step in for him? Abby and Morris wrestle with the strange case of a car crash victim. Having made a change in her life, Sam finds herself enjoying a few new perks. Neela has unexpected visitors, with even more unexpected news.

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.

Luka has a very bad day: New nurse manager Eve Peyton notices he doesn't want to work with Sam and tells him so. At the end of the day he's drunk and Abby takes him home.

Pratt's half-brother tries to get him to make ends meet 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.

Neela treats a religious teenage girl who turns out to be pregnant. Abby and Kovac struggle to figure out what to do with her unexpected pregnancy.

When is it time to go out on a limb? Armand Assante guest stars as a patient who makes Sam an offer she might not be able to refuse. Luka must calm Abby’s baby-related fears after an incident at the hospital places everyone at risk. Kerry makes a difficult choice, and Neela joins a support group.

In the 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.

Sam and Luka go on the search for her runaway son, Alex. Meanwhile, Pratt and Lewis guide Abby, Neela and Ray, who have become R2's, on how to teach the new interns.