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.

Carter finds himself struggling with County's new technology and procedures. After becoming frustrated with the in vitro-fertilization, Banfield and her husband discuss adoption as an option. Sam's mother arrives in an altered state of mind.