The dead body of ten year old Daniel Lanham is found buried in Harwood State Park in Pennsylvania. Missing since November when he and his father, Joseph Lanham, were camping, Daniel was kept alive over the winter before being killed in March. Experienced hiker and camper Joseph was and is a suspect, most notably now since he purportedly stopped looking for Daniel around the time he was killed. Reviewing the crime scene, the BAU find another dead body of a boy around Daniel's age, who also was killed months after his abduction. Reid suspects that the serial killer would have murdered more boys over several years over the entire course of the Appalachian Trail, and that he lately has confined himself to a smaller portion of the trail due either to his age or a physical disability which is making him less mobile. The unsub is working like an animal in the woods, hibernating with the boys over the winter before disposing of them. Meanwhile, adolescent brother and sister Robert and Ana Brooks, camping with their parents, are abducted in the same area. The BAU have to work fast since Ana was probably abducted out of circumstance of being with Robert rather than a want of the unsub. Ana's abduction means the unsub may have to improvise off his plan in dealing with an unwanted captive, and hopefully slip up in doing so. Joseph, knowing the area well, wants to assist in the investigation.