Killer: The "Unsub," or unknown subject, is tracked down by the FBI's specialized team called the Behavior Analysis Unit, which uses behavioral science and technology to find the killer. Each episode of the CBS show is devoted to a different unsub. Modus operandi: Hacking, slashing, slaying, shooting, eating. You name it, the BAU has seen it. Still at large? Most episodes are settled by the BAU finding and locking up the unsub before s/he claims the next victim, but a few extra creepy unsubs have eluded even this task force.