ER

The 15th and final season of ER begins with the devastating repercussions of the ambulance explosion. As Morris and Neela do everything they can to save a wounded colleague, Abby treats a young girl injured during the blast.

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.

Abby's first day as an attending is bittersweet. Neela is hurt when she finds out Abby's news from someone else. Abby and the new ER Chief argue over how to treat a gunshot victim. Abby comes to Sam's aid when she faces a nurses' disciplinary board.

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.

It's Halloween night, and the interns continue to be paired with the residents. Gates's teaching methods with Daria, and her responses, belittle Sam. A school fight results in a stabbing and a nose that won't stop bleeding, with Brenner treating the victims and being deeply affected by the truth behind their confrontation. The staff, especially Neela, are enthusiastic about a surprise visitor. Gates gets locked in a maintenance area with a quiet young boy.

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.