The team travels to a North Carolina town where one woman was found badly injured and another is missing, and discovers those may not be the only victims.
Castle and Beckett uncover a story of betrayal and obsession when they investigate the death of a teenage boy.
Carter's new medical student (Chad Lowe) constantly disappears to work on research; Benton and Carla name their son; Greene hires a new desk clerk.
Greene's success with prospective ER interns causes Anspaugh to offer him a tenured teaching position; angry with Benton, Carter wants a transfer.
Dr. Benton undergoes an emergency operation; Dr. Ross helps the mother of a teen with cystic fibrosis deal with her son's attempt to control his treatment.