Casey Nelson

The team head to Canada to investigate the disappearances of a number of homeless people, drug users and sex workers and uncover something horrific in part one of the season finale.

The BAU team heads to Texas to track a serial killer targeting illegal immigrants attempting to make safe passage into the U.S.

When actor Grady Bridges (Colin Hanks - "Orange County," "Roswell") invites Summer and Marissa to his birthday party, the girls take Ryan and Seth to Los Angeles to join in the festivities. At the party, Summer is thrilled to spend time with Grady, but Seth is not as happy. The situation is reversed when Seth meets sexy Kate (Paris Hilton - "The Simple Life"), and it's Summer's turn to be jealous. Afterwards, the gang heads back to Orange County, where Ryan has a hard time keeping Luke and Julie's affair a secret from Marissa.