It's been ten years since a Columbine-style high school massacre, and the survivors are returning for a ceremony of remembrance and reflection. While the school shooter/bomber died in the act, a new killer is now on the loose - an UnSub targeting survivors using the same methods as the original attacker. As the BAU team races to profile the UnSub, Dr. Reid makes a chilling discovery: whoever is doing the killing seems to be suffering from a rare disorder where he can not feel pain.