Stephen Walker

Stephen Walker is a Supervisory Special Agent with the BAU, who joined the team in Season Twelve to assist in the manhunt for Peter Lewis, a.k.a. "Mr. Scratch".

Background
Little is known about Walker at this moment, other than he was an experienced profiler, with about twenty years under his belt, and a member of the FBI's Behavioral Analysis Program before his transfer to the BAU. He is also married to a woman named Monica and has two children with her, Maya and Eli. He met Emily Prentiss, then the chief of Interpol's London office, during his line of work. He was also mentored by David Rossi. Walker's first case concerned a terrorist cell in Belgium, and three agents were sent undercover to infiltrate it. However, Walker's profile was wrong, and this resulted in the deaths of the undercover agents. He eventually moved on from the trauma and improved as he went along in his career.

Season Twelve
Walker is recruited into the BAU by Prentiss, who had become the Unit Chief of the BAU following the resignation of the Unit's previous chief, Aaron Hotchner. Prentiss had been able to expand the team's budget to allow an eighth member into the roster, and Walker was selected for his expertise.