While posing in front of a mirror, a popular 16 year old girl named Tara Harris is killed. Her assailant takes her picture and the posts it to Twitter with the note "Fear me" and the hashtag #selfie
The tweet goes viral, gaining over a million hits and retweets.
While this is going on, someone is superimposing a creepy graphic image of a face in the mirrors behind other social media photographs, causing them to think that they might be the unsub's next victim. They refer to the unsub as "mirror man".
While the BAU investigates Harris' murder, another person who is popular on social media - Alexander Chase - is killed when the unsub comes up behind him in his convertible and shoots several nails into the back of his head and neck. The unsub then uses the nail gun to create a pattern of a hashtag on the seat back.
A third person - Daniel Osborne - taunts the unsub on social media, and then later becomes the unsub's third victim, when he too is killed by a nail gun in his home.
The BAU suspects that the unsub might be Connor Holt, a high school student. When they bring him in for questioning, he confesses to having created the "mirror man" story, but not for creating the superimposed images on photos. This leads the BAU to suspect that the unsub is someone who looks up to Connor.
After learning of the unsub's profile, Connor identifies the unsub as William Pratt, a friend and classmate.
When the BAU confronts Pratt in a mall parking lot, he grabs a woman and holds a nail gun to her head. The team tries to talk him down, but a media truck comes by.
Realizing that he's getting publicity, Pratt shoots a nail into the neck of his hostage, and Morgan shoots him.
Both Pratt and the woman are taken to hospital where they undergo successful treatment.
Meanwhile, anxious to show his girlfriend that he can be depended upon, Morgan brings Savannah to the house he's been remodeling, and asks her to move in with him. She accepts.