Reid and Prentiss are sent in undercover to investigate alleged child abuse at an isolated property which is the home of a religious cult after an anonymous 911 call states that the cult leader, Benjamin Cyrus, (brilliantly played by Luke Perry) is having sexual relations with underaged girls in the compound.
With Prentiss and Reid posing as officials investigating child abuse, the real aim is to not only ascertain whether or not this is true, but also to look into the cult as a whole. Naturally, things go horribly wrong and Prentiss in particular is in grave danger when her cover is blown (although Reid's remains intact). The rest of the BAU, along with a plethora of other law enforcement agencies, are planning a raid on the compound, but when Cyrus gets wind of this, he imposes a lock down and unleashes a cache of weapons which make it pretty clear that he has no intention of being taken alive ... and the same goes for his 'loyal' followers as well.
Not only great work by Luke Perry, but also terrific stuff from Paget Bewster and Matthew Gray Gubler. Don't miss this one!