Title: Little Girl Lost
Air Date: May 4, 2009 at 12:00 AM PDT
A 2-year-old girl goes missing, and Beckett is called in to assist with the investigation. She's in for a bit of a shock, however — the FBI agent in charge is none other than her ex-boyfriend, William Sorenson. The two of them try to put aside their unresolved feelings as they race to find the girl, but when Castle inserts himself into the investigation, competition quickly heats up for Beckett's attention.