In Season 8 of 'Criminal Minds', the experts of the FBI's Behavioural Analysis Unit (BAU) crack cases by getting inside the heads of America's most twisted perpetrators in 24 gripping episodes. The team welcomes a new member, linguistics expert Alex Blake (Jeanne Tripplehorn), while they uncover one of their grimmest challenges. A chillingly familiar series of slayings reveals the existence of the "Replicator", an obsessed killer who taunts the team by re-creating bizarre murder methods from past cases. But even the most devious criminal mastermind will have trouble eluding the grasp of sharp minds like unit chief Aaron Hotchner (Thomas Gibson), profiling expert David Rossi (Joe Mantegna), scientific genius Dr. Spencer Reid (Matthew Gray Gubler), Special Agent Derek Morgan (Shemar Moore), Special Agent Jennifer "JJ" Jareau (A.J. Cook), and technical analyst Penelope Garcia (Kirsten Vangsness).