Juan Carlos Cantu

Gideon, Hotchner and their team head to Mexico to aid in the investigation of a serial killer who preys on the elderly.

Dexter hires a nanny; Debra is annoyed with her new partner; Quinn continues to investigate Rita's murder.

Special Guest Star Michael J. Fox. -- Elliot finds herself perplexed over a simple procedure that leaves her questioning her career path. She goes to seek Dr. Kevin Casey's (guest star Michael J. Fox) advice but becomes frustrated when she learns that the epiphany toilet, which the Janitor secretly installed on the roof, is getting more attention than she is. Meanwhile, Turk asks J.D. to be his best man at his wedding, which sends J.D. momentarily into sheer bliss, until he hears a phone message that makes him question his friendship with Turk.

The team investigates a car explosion with a connection to an agent who went missing six months earlier; Gibbs asks NCIS Special Agent Alex Quinn to shadow his team.

While visiting Mexico with her family, a woman becomes a victim of foul play; when the International Response Team investigates the woman's husband, he flees, making him the prime suspect.

Richard must make a difficult decision.