Gideon, Hotchner and their team attempt to catch a suspect who has poisoned multiple residents of a small town.

After determining that the suspect used LSD and "ruphies" to poison the town residents, the team must next identify what type of poisoner they are dealing with, such as vengeful or prankster, in order to ascertain his motive.

As they piece together a profile, they become certain that the poisoner intends to strike again and set out to stop him before he can claim any more victims.