It's the first day of Carter's internship. He has a 36 hour shift and overnight he has to cover the ER, the ICU as well as the surgical patients.

While Mark is anxious about Susan's return from her holiday, Doug and Carol ride along with the health mobile.

Encouraged by Carol, Mark finally asks Susan out. Benton tries to save a boy, despite the fact Doug thinks he's brain dead.

Carter and Lucy are discovered and the staff struggles to save them and go on with normal patient care.

Corday rushes through a surgical procedure in order to take off on a romantic weekend with Greene. She is later called back to the hospital after her patient suffers complications. Abby's mother, Maggie, who suffers from bipolar disorder (manic-depressive) and refuses to take her medication, unexpectedly visits Abby at the hospital and wreaks havoc on Abby's life.

Carter is overwhelmed by patients from a rock concert riot. Benton's former girlfriend is killed in a car accident. Newly promoted to chief resident, Chen panics and misdiagnoses a patient. Kovac angers Abby by flirting with a waitress.

Dr. Susan Lewis arrives, looking for work in the Chicago area again. Greene hires her, over Weaver's objection. Chen nervously attends a risk management review, accompanied by the unforgiving Weaver, to discuss a patient who recently died under Chen's supervision.

Corday's ordeal, caused by the recent infection-related deaths of several of her patients, worsens when she is closely observed by a stern taskmaster. Corday is outraged when a county investigator accuses her of deliberately euthanizing the patients, who all happened to be elderly.

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.

Dr. Weaver bends the rules and treats the Alderman's lover for syphilis. Dr. Kovac's patient claims she was sexually abused at a boot camp for troubled youth. Dr. Carter treats a women with a nasty personality.

Carter's day shift and Pratt's night shift (his final shift at County) are intercut. Both men have extremely busy days. Doc Magoo's burns down. Luka calls Carter from the Congo and asks for help. Carter decides to go. Pratt decides to stay at County. In other parts of the hospital, Romano has his now-useless left arm amputated.