Kelly McCracken

JD's older brother Dan visits him, and the two men re-examine their relationship, Dr Cox teaches Turk an important lesson, and JD and Turk spend Halloween night at a bar.

Having dated seriously for a week, Marissa and Ryan are progressing slowly. Summer tries to deny her true feelings for Seth, while the case against Kirsten's father Caleb continues to cause friction between Sandy and Kirsten.

The BAU travels to Dallas to assist in the search for a murderer who scares his victims with missing flyers that display the soon-to-be victims' photos. Also, SSA David Rossi returns to the BAU from retirement.

A scientist is deliberately exposed to a deadly toxin at a high-security biological research facility. Before she dies, she calls Jane to ask for his help in finding her killer. Once the agents have arrived on scene, however, another empty flask of the toxin is discovered, suggesting all those inside the facility have just hours to live.

A determined officer joins forces with an undercover agent to bring down a manipulative man who has attempted to kill his ex-wife three times.