Shiloh Nelson

Walden reconnects with Kate and is sure she's "The One" – that is, until he meets Vivian (guest star MILA KUNIS – That '70s Show, Black Swan), a beautiful, free-spirited world traveler who shows up on his doorstep. Feeling an instant connection with Vivian, he soon becomes convinced that she's "The One." Meanwhile, Alan and Gretchen grow closer.

The BAU investigates a double homicide and kidnapping in New Hampshire; Rossi's plans to elevate his relationship with Krystall don't go as planned.

Avery welcomes D.B. Russell to the team as they investigate a burglary/homicide committed by someone who hacked the home's security system remotely. Also, Avery considers moving to a new position within the hierarchy of the FBI, Krumitz is a witness in his sister's trial, Elijah deals with a delicate family situation and more is revealed about Nelson's and Raven's backgrounds. Ted Danson joins the cast as D.B. Russell, the new Director of Next Generation Forensics, who transfers to Washington, D.C. from Las Vegas.

Department of Justice Agent Lance Hamilton asks Sam for assistance in locating a former U.S. Border Patrol tactical officer who disappeared following a threat by the cartel.