Atlanta PD has invited the BAU in for an equivocal death investigation, that of investigative journalist Albert Stillman, who died being run over late one evening as he wandered into highway traffic. An eyewitness who tried to help Stillman just before he was run over states that he was waving his arms in the air yelling, "get them off me", this depiction which goes against Stillman's history of no mental illness. Reluctantly, Stillman's editor, John Carlson, discloses that Stillman was using heroin as medication for a back problem. Stillman was scheduled to meet with a source on a story concerning vaccinations when he vanished for three days just before he died. Garcia learns that another person associated with the case is a Dr. William Suri, a research scientist of entomology, who is later found dead, shot to death. Upon investigation, the team discovers that both Stillman and Suri were abducted - meaning that they are dealing with a serial killer - and had minute bite and deep self-inflicted scratch marks. They thus come to the conclusion that the unsub has delusional parasitosis - the belief that he is infested with bugs - and is looking for people to support his delusion by making them feel what he feels. When they don't support the delusion, he kills them. Based on that theory, the team believes his next victim will be someone in that vein, someone who may have a similar delusion. Locating such people may be easier than getting them to cooperate in the investigation, even if there is the threat of what happened to Stillman and Suri happening to them.