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.

Pratt and a new doctor on the scene disagree on how to teach the interns. Gates treats a young woman with serious heart problems. Abby heads to Croatia, and ponders whether and how to tell Luka about her unfortunate choices. Sam discovers that Julia has moved on in more ways than one.

When a drug deal goes bad, two brothers sustain serious injuries and are brought to the ER. Tensions continue between Gates and Sam, coming to a head when Tony is the last to know Alex is about to be released from the hospital. Neela has to tell a young girl with sickle cell anemia that she must have an operation, and the case leads her to consider specializing in pediatric surgery. A feisty patient takes Morris into her confidence. Banfield ponders her choices about expanding her family.

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.

A mysterious illness leaves little hope when a group of homeless kids enter the ER and one of them believes that Neela is a guardian angel in blue; Abby and Kovac clash over a possible case of domestic abuse; Pratt makes a shocking discovery about his brother, and Weaver is unexpectedly called into action when her television appearance becomes a real emergency.

Kovac and Gates find themselves with a moral dilemma when a woman comes into the ER with acute liver failure; Neela finds herself questioning what is right when Manish decides to give up a kidney to a complete stranger. Meanwhile, Ray fights to get to the bottom of a cheerleaders accidental fall; Abby gets a prediction for her future; and Alex's troubles continue to intrude on Sam's work life.

Morris and Pratt cram for their medical boards when Morretti brings in a new attending physician to help with the load. Sam and Abby work on an attention-hungry patient who comes into the ER with elusive symptoms.

Everyone at the ER is happily surprised to see Luka back from Croatia. Great news awaits Neela. Sarah once again needs rescuing by Tony, and patients are causing problems for Morris.

It's time for changes at the ER when Anspaugh makes an unpopular decision. Abby has old demons to fight with, which distance her from friends and family. Even Luka seems to be at a loss to help Abby. Love is in the air when a secret romance blooms between two doctors.

Neela's short visit in Ortho turns into a game of hockey. Bettina wants to take her relationship with Pratt to the next level, but Pratt is not keen on the idea. Gates and Sam disagree over a patient. Julia provides some spiritual guidance in order to ease a prison doctor's bad conscience.

Neela, worn out after being on shift for over 24 hours, has to make a quick decision regarding an accident victim's torn aorta. Sarah's grandparents are in town, and Hank is rushed to the ER after collapsing during an outing. Gates tries to convey to Sam that his feelings for her are serious.

Kovac is in Chicago looking for hospice-care work. Neela's aorta surgery has caused an infection in her patient. Abby treats a teen who has been beaten up. Brenner continues to cause problems for the ER staff.

Morris faces a complicated case involving a young girl hit while riding her bicycle. Gates finds it very difficult to let go of his feelings for Sam. Neela becomes quite flustered when Brenner returns from Australia.

Dr. Weaver is in a difficult situation when an alderman tests positive for syphilis. Dr. Carter is impressed when he meets a man who runs an inner city clinic.

Abby's troubled brother is missing. A car runs into a crowd of teen girls. The alderman with syphilis gives Dr. Weaver a promotion. Dr. Lewis looks forward to a blind date.

Neela starts a new job in the emergency room after working at the convenience store near the hospital. On Neela's first day, Pratt expects the interns, Abby, Ray and Neela, to take on a large patient load during their shifts. Pratt turns processing the patients into a competition, in which Ray is clearly going to be the winner.

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.

Gates is assigned to the case of a closeted gay man whose partner clashes with his family; Neela meets her new surgical chief, Dr. Crenshaw; and Pratt must cope with the flood of new interns.

Abby and Kovac discover both the joys and difficulties of raising a newborn; Morris is wrongfully accused of being a child molester; Pratt has his trial-by-fire when he has to handle the ER alone, juggling multiple traumas, teaching duties and a troublesome intern. Neela continues to be the target of her difficult supervisor, and Sam discovers her sons latest extra-curricular activity.

A blizzard strands a family in the snow and Abby and Pratt quickly try to save the family. A gang shooting challenges Morris and Pratt. Meanwhile, Kovac and Abby begin making wedding plans, but their engagement might not be very secret; Gates struggles with the reappearance of his father and the possibility of losing Sarah; and Neela becomes jealous when Dubenko brings in a new surgical intern.

Moretti begins to make his presence felt, as he implements changes in the way patients are seen. The ER staff differ on how procedure when a patient comes in with a bullet in him needed as evidence. Neela finds herself the object of more attention that she wants, or needs. Abby had passport woes, and struggles with the changes being made. Pratt and Morris find themselves forced to defend their actions, Hope prepares for a new mission, and Gates finds himself labeled the reject in his new assignment.

Moretti reassigns Gates back to the ER and treats a couple involved in a car accident. Morris prepares to take his written board exams. Neela is assigned a young genius intern. Kovac plans to extend his stay in Croatia while Abby struggles with single parenthood.

Abby is back from rehab and finds herself the object of scrutiny. She confesses to Pratt that Luka might stay in Croatia longer than planned. Harold seems to have won over Neela's cousin. Multiple victims from a fire fill the ER.