Everyone in the ER is trying to cope with the loss of their colleague. The staff feels defensive toward the new Chief and her tough disposition. Gates and the new interns treat a bio terrorist who has a lethal secret that endangers them all. Neela makes a great effort to get Dubenko back on the surgery staff, and gets help from an unexpected source.

Dr. Banfield defends herself during a mugging. Dubenko returns to work, due in no small part to Brenner's organized protests. A young gymnast comes into the ER with injuries consistent with a fall, but Banfield and Gates each think a different family member may actually be to blame. Sarah neglects to ask Gates's permission before getting her tongue pierced.

Chaz, now a med student, begins his ER rotation. Morris takes him under his wing and shows him some risky procedures, endangering a patient and raising Banfield's ire. Neela becomes upset when Banfield questions her authority and skills in front of her intern. Gates invites Sam and Alex to move in with him and Sarah.

As a snowstorm hits Chicago, Sam's son Alex crashes a car and ends up in critical condition in the ER. Neela gives a deposition in the malpractice suit against her. Banfield and Morris are both at a medical conference in Omaha, and when the snow cancels all flights out, they share a memorable and surprising evening.

A package for Morris from his deceased father is delivered to the ER. Sam has some anxiety over Alex being removed from the ventilator. A woman with a high-risk pregnancy worries that she will be deported. An old friend returns to celebrate the holidays.

As Carter prepares to open a new facility for the underprivileged, some old friends/colleagues gather. Rachel Greene, Mark Greene's daughter, applies for an internship at County.