"I'm your biggest success story."
Finster was born on February 12, 1964, likely in Seattle, Washington, where he lived until the events of "Magnificent Light". He suffered from synesthesia, a condition where triggering one cognitive sense, such as sight or taste, might trigger a reaction in another. In Carl's case, his condition allowed him to visually "see" the words being spoken by a person who is addressing him. These words were colored in certain colors, which helped him determine the credibility of the speaker. For his entire life, Finster maintained a system of colors that he associated with certain emotions: white determined the speaker was being honest and sincere, yellow determined that the speaker was lying, and red determined that the speaker was truly "evil". As an adult, Finster tried to suppress these hallucinations by wearing tinted sunglasses, which presumably didn't help. On September 19, 2010, he got a job at a credit-card workplace, in which he responded to phone calls made by customers. However, on July 2012, he was fired by his boss, David Cooper, after becoming increasingly violent towards customers and coworkers.
This brought distress to him and he was contemplating suicide when he came across a popular motivational speaker, Barry Flynn, whose inspirational speeches and teachings restored and strengthened his self-confidence to the point where he believed that his condition was a superpower. As a result, he developed a fantasy world in which he was a superhero, using his condition to single out liars and "evil ones" and brutally kill them. This delusion was further enforced by an occurrence where Finster overheard a man whom he described as "evil" and tried to call the police on him, but after he was shot down, a mother and daughter were killed by a carjacker; Finster was fully convinced that it was the same man. Also in this fantasy, Flynn was his sidekick. Finster eventually initiated his "mission", ritualistically stabbing a man named Lincoln Bell, who resembled Cooper, to death. He then left a message meant for Flynn behind, reading "Hear your evil, see your evil".
When Flynn comes to Seattle for a conference, Finster feels that it is his opportunity to gain his "sidekick". He attends the conference and is one of the several attendants to stay behind as part of a bonus one-on-one talk with Flynn himself. However, Flynn is unable to attend, and Finster, determined to prove his loyalty, follows another attendant, Cynthia Strobl, home and stabs her to death, leaving the same message behind as he did with Lincoln Bell. Later deducing Flynn's location at a bar, he convinces another man, Ricky Lopez, to lure him out. Lopez does, and when Flynn is outside, Finster knocks him out and abducts him, with Lopez unable to witness the whole thing as he went back into the bar immediately afterwards. Flynn later wakes up at Finster's house, where Finster introduces himself and states that he won't let him go until he "understands". Later, Finster purchases some food for himself and Flynn, whom he explains his condition and his mission to. When Flynn makes a comment on Finster's "mission", asking when it stops, Finster responds that it won't. He then arrives at his workplace and gathers all of the names and addresses of the customers that called him, intending to kill those he saw as liars and evil. David Cooper, his former boss, spots him and, fearing that Finster is intending to commit a workplace shooting, approaches him and talks to him. Finster asks why he was fired, but as Cooper responds, he instead looks at the visual words, which upsets Cooper, who tells him to leave, to which Finster accuses Cooper of being jealous of him before leaving.
Finster later takes Flynn to the house of Janet Dodd, one of the customers that he singled out as evil, and waits for her husband to leave. Flynn tries to talk him down, but it fails to work and the two break into the Dodd house, with Finster killing Janet in front of Flynn's eyes. He then leaves a new message behind: "Hear your red, see your red." In an effort to stop Finster, Flynn pretends to understand the mission and wishes to participate in it, only asking Finster to let him loose from his bonds in return. He agrees to do so only after he kills Howard Jeffson, another target. The two arrive at Jeffson's house, only to find Jeffson not home and instead occupied by Stephen Caldwell and his family, who rented it. Finster is initially unconvinced until he sees Stephen's words, which are in white. But when Stephen lies to him, saying that the family won't call the police, Finster finds out and decides to kill him anyway, ordering Flynn to take out his ceremonial knife. When Flynn tries to talk Finster down again, Finster is horrified to see that Flynn's words are in red. Angered, he injures Flynn with the knife and tries to kill him, but the BAU burst in, rescue the family, and hold him at gunpoint, ordering Finster to drop the knife and a handgun that he had also been using. Finster refuses to comply until Morgan tells him of the carjacker, who actually wasn't the man Finster overheard. Finster believes Morgan, as his words are in white, and drops his weapons, allowing the BAU to arrest him.
Finster's victims were targeted for various reasons: Lincoln Bell resembled his former employer David Cooper, Cynthia Strobl was killed to prove his devotion to Flynn, and Janet Dodd was a customer whom Finster determined as being "evil" by the color of her words in his hallucinations. All three were blitz-attacked and killed in their homes at night by having their carotid and femoral arteries slashed and then stabbed repeatedly in the chest, even after death. In the killings, he used a ceremonial knife as means to make their deaths look sacrificial. During his latter killings, Finster targeted the customers he talked to, specifically those he deduced to be liars and pure evil. His signature was leaving messages written on a nearby wall in red paint after killing his victims. With his first two victims, he wrote "Hear your evil, see your evil". In the case of Janet Dodd's murder, the message was "Hear your red, see your red" as a reference to the red visual words he would see that signifies one's true evil. During the attack on the Caldwell family, Finster also used a handgun to keep the victims compliant.
While it was originally thought that Barry Flynn was a suspect, it soon became clear that the unsub is one of his followers, who suffers from erotomania. He is obsessed with Flynn, his latest captive, and he may believe that Flynn is also in love with him. It should be noted that erotomania has very little to do with sex, and it instead involves more of a romantic or spiritual connection that erotomanics crave. Victims of this delusion tend to come from a higher social status and have done very little or none to directly stimulate or encourage such a delusional belief, so it is likely that Flynn and the unsub have had no previous contact, and that the latter's infatuation began from afar, considering Flynn's celebrity status as a motivational speaker. The patience required to commit his crimes describes the unsub as a male aged in his late 30s to 40s, who is single and socially immature, therefore a typical loner with poor social skills. Although he is capable of holding down a job, he most likely neglects his duties, instead focusing more on his obsession. He spends much of his time living in his delusional fantasy world, and he may have been tracking Flynn for quite some time. With erotomania, the most likely recipient of violence is the person standing in the way of the desired object, and so, it is possible that the unsub witnessed some sort of interaction between his first two victims and Flynn, killing them in a jealous rage, but there is another possibility that the unsub killed them to prove his devotion to Flynn.
The weapon that the unsub uses in his killings has a ceremonial quality to it, which means that he views his victims as sacrifices, and the messages he is leaving behind at the crime scenes may be meant for Flynn. In his head, when Flynn came under his control, the situation became especially precarious. If the unsub is under the delusion that Flynn also cares about him, then any misstep by Flynn that contradicts the belief that the two are in a relationship could lead to more victims or even Flynn's own murder to prove that they have a special bond. With each passing hour, it is becoming very unlikely that Flynn will match the unsub's expectations for him, so it is important that he is found in safe condition quickly.
- November 23: Lincoln Bell (message read "Hear your evil, see your evil")
- November 24: Cynthia Strobl (message read "Hear your evil, see your evil" like the previous victim)
- November 25:
- Barry Flynn (abducted, non-fatally slashed his abdomen, and attempted to kill; was rescued the next day)
- Janet Dodd (message read "Hear your red, see your red")
- November 26: The Jeffson house standoff:
- Howard Jeffson (intended)
- The Caldwell family (incidental; briefly held hostage; all were rescued)
- Stephen Caldwell (father; assaulted and attempted to kill)
- The unnamed mother
- The unnamed daughter
- Note: Finster had also compiled a hit-list of at least 150 names of people that he intended to kill, although whether or not he was actually going to kill all of them is unknown.
- Raphael Sbarge, the actor who plays Finster, also portrayed Davis Scolfield, a serial killer and abductor featured in the pilot episode of Suspect Behavior, the short-lived Criminal Minds spin-off.
- There was another color in Carl's system of colors, green, which could be seen when Carl was reading David Cooper's words. The meaning of green in Carl's system is never elaborated on and was not an important aspect in the episode's plot.