As The Prince of Darkness continues his murderous rampage across California, the BAU go after him to save Detective Spicer's daughter from him.
Morgan and Det. Matt Spicer are unable to reach Spicer's daughter, Ellie Spicer, before she is kidnapped by the unub, who has been raping and killing during blackouts for twenty-six year. In the kidnapping process, Morgan and Spicer's sister, Kristin, are beaten, and Spicer himself killed. Spicer's parents were the unub's firt victims twenty-six year ago. Ellie, who quickly undertands her role in the unub's twisted fantasy, ends up being more resilient than the unub firt believed. Meanwhile, the BAU, with information from Kristin, believe they undertand why the unub kidnapped Ellie and has probably kept her alive. The BAU also believe they have a mean to at least contact the unub. In doing so, an uncomfortable J.J. is requested to do some work outside of her responibility. Reid, in the meantime, finds an earlier murder which he believes is also connected to the unub...

Behavior Analysis Unit (BAU) is by studying the criminal mind to look for criminals , and bring to justice the FBI a branch . BAU to take over the cases of mostly comic crime , members from the series of modus mode to deduce the killer 's gender, race, age , occupation , and other elements of the suspects in the process of " profiling " to help the police to bring perpetrators to justice . However , it is regrettable that JJ will exit in the new season .