Walter Resden, an alleged serial killer who eluded Horatio 11 years ago in New York and again more recently in Miami, returns, and Horatio is horrified when he learns that the man is seeing the daughter of one of his alleged victims. The hunt for Resden begins when a man's body is found in a volleyball pit during a match and a house key is discovered in the victim's throat. Back at the lab, Natalia fears that she may be pregnant with Delko's baby.