The hospital suffers through a series of power outages. Carol's decision to send Doug a fax about her pregnancy is thwarted by the power outages. The staff is on alert after a raped and beaten patient is found in a hallway. Romano begs Corday to stay in trauma. Carter and Roxanne break up. Carter and Lucy treat a pheromone saleswoman.

Dr. Greene and Corday bond with their parents, Lucy cares for a patient with a psychotic break, and Valentine's Day celebrations in the ER end tragically for one of the students.

Abby and Carter travel to Oklahoma to rescue Abby's mentally ill mother and bring her back to Chicago. In Chicago, Maggie suffers from a sleeping pills overdose. At County General, Kovac frantically revives her. Benton treats a college student injured in a fraternity prank.

A new medical student, Michael Gallant, arrives in the ER. He's supposed to be working under Dr. Carter's supervision but his grandmother is unwell. Elizabeth Corday is convinced that other doctors are refusing to work with as a result of the mysterious deaths.

On a busy Halloween night, Carter and Abby are the only staffers in costume when victims of an apartment building fire pack the ER. Corday takes on a new med student for a surgical rotation - Paul Nathan, who suffers from Parkinson's disease and decided to pursue medicine after being diagnosed. Despite a difficult first day, both professionally and medically, Nathan makes a difficult diagnosis. Romano's rehab lags behind his expectations, and he begins to doubt his role in surgery is no longer an option.

Abby and Neela are assigned to a month-long rotation in the neonatal intensive care unit where they experience emotional roller coasters while caring for the sick infants.

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.

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.

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.

Kovac and Gates treat a girl who appears to have been assaulted. When the police are no help with Ames, Kovac decides to confront the problem himself; Morris and other doctors work on a patient with an ice pick in his ear. Meanwhile, Ray tries to keep his new relationship a secret and Pratt can't fully deal when his half-brother officially comes out. Also, a new male nurse arrives.

Dr. Kevin Moretti, an ICU specialist bent on change, joins the ER team. Change comes elsewhere as Luka and Abby adjust to being husband and wife, Pratt tries to be a new man to his lady friend, Morris and Hope take things to the next level, and Ray goes missing. Later on, Luka gets a troubling phone call.

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.