This episode reveals the shocking history of the Doomsday Killers. Professor Gellar was dead all along and Travis was the only Doomsday Killer and the true main antagonist of this season. Dexter receives help from an unexpected source while hunting the Doomsday Killers and staying one step ahead of Homicide; Debra discovers something new about herself in therapy.
Dexter and Travis are together in the abandoned church. Dexter asks Travis about Gellar's location and the next tableau but claims he doesn't know. The painting of the tableau has "2LOT" written on it. While Dexter hunts around Travis nearly passes out.
Dexter finds Travis a hotel for him to hide out. Dexter gives Travis a little medical attention and tells him he is not to leave the room.
Dexter looks up 2LOT online and finds it is an abbreviation for the Second Law of Thermodynamics - the tendency of order to become disorder or chaos. Dexter found a Miami South University parking pass in the church and sees online that a Professor Casey has written a book 2LoT tales and is a crusader for atheism.
Deb talks to the psychiatrist about Dexter. The conversation drifts to her father and her past relationship with a serial killer. The therapist wonders if they should meet more than once a week.
Before Deb's briefing, Masuka tells the guys about Quinn getting loaded and proposing to strippers. Angel explains that the likely next tableau, The Bowls of Wrath, has to do with punishment poured on the people. Gellar has recently updated his blog, saying that something big is happening in six days. Louis tells Deb he's going to try and take a stab at finding the IP address Gellar used to update his blog.
Angel shows up at Quinn's place where he's passed out on the floor. Quinn's gun is missing. He thinks it might be in the backseat of the car belonging to a stripper he hooked up with. Using GPS they locate his cellphone across town.
The father of Jessica Morris tells Deb he'd like her to re-open his daughter's case. He's found out that her sternum was cracked.
Masuka tells Louis that he should tell Jamie how he feels and if she likes him back she'll take care of any of Angel's objections.
Dexter brings Travis some food and tells him about the blog. Travis thinks a line about "all those following false prophets" in the entry was directed at him. Dexter mentions Professor Casey.
Quinn drops by to see the woman he hooked up with, but it turns out not to be the hot young daughter, but the much older and not so attractive mother who greets him enthusiastically. She isn't a stripper, though he actually met her at the Waffle House across the street.
They retrieve Quinn's sidearm and cellphone, and leave. Angel's car breaks down on the way back to the station. They begin to argue and physically fight.
Dexter drops by one of Casey's classes. He sees that Casey has late office hours that night. After class he tells Casey that he might be in danger. Casey brushes him off.
Dexter sets up his kill room at the abandoned church. He tells Harry it's important to him that he kills Travis's dark passenger.
Travis tells Dexter that Gellar convinced him they were chosen by God. He tells him when Gellar's gone they can start again. Travis spots Gellar outside Casey's office. Dexter takes the elevator up to grab Gellar, leaving Travis downstairs in case he doubles back. The elevator shuts off and Dexter tries to escape through the shaft. Travis helps him escape, but when they reach Casey's office it looks like he's already been taken.
Back at the hotel Dexter tells Travis they can still stop Gellar. He wants Travis to start sending him messages through the blog.
The next day Deb tells Dexter the Doomsday Killers has struck again. He is called to the MSU campus where Casey's body is lying on a stage minus his right hand. His blood has been drained and the Alpha and Omega symbols are carved into his abdomen. His stomach, though, has been removed. When Masuka lifts Casey's arm buckets containing his blood pour down on top of them like the earlier "angel tableau", this scene has been booby-trapped.
Travis wakes with a start. He walks into the bathroom and sees a message written in blood: "BRING THE FALSE PROPHET TO THE CHURCH." Casey's missing hand is in the sink.
Deb tells the psychiatrist about Dexter being related to Brian Moser. She wants Deb to take responsibility for her actions and points out she has a history of picking dangerous men.
Empowered by her therapy session, Deb tells Maria if she has a problem with her re-opening Jessica Morris's case she should fire her.
Maria gets into a car with Matthews and we learn that he was the one who was with Jessica when she OD'd. He did what he could to save her but would have ruined his career if he stuck around for the police. He says "we have to stop her".
While Travis washes off the blood he gets a call from Dexter. Travis mentions the expression "the writing is on the wall" from the Bible. He says Gellar is sending another message but doesn't tell Dexter about the writing in the bathroom. He says Gellar contacted him and wants to meet in the church.
Dexter asks Deb whether they are okay. She says she's working on herself.
Masuka brings Deb an address Louis got from the IP address. It's from an unsecured network. The owner says he has no idea who uses his signal, since its range is about 900 feet. Louis points out that one could boost the signal and add a mile or two. We see the church in the distance.
Louis has Jamie over to his fancy apartment. He tells her about Angel and they begin to kiss. We see them end up in bed. We also see that Louis is in possession of the arm Masuka's previous assistant took from evidence and sold on-line.
Travis and Dexter sit outside the church. The plan is for Dexter to go in the back way after Travis walks in the front door. Gellar yells at Travis, who says he doesn't believe in a god of violence. Gellar wants Travis to repent for his sins. Gellar tells him to "come to me" and he seems to move in for a hug.
In the back as Dexter prepares his kill room, Harry asks what he gets out of removing Travis's dark passenger. Dexter says he cares about being a good father.
Dexter walks into the church and finds Travis lying on the floor. He appears to be unconscious. Dexter finds a trap door and walks down the stairs. He finds Gellar's rigid and frost-encrusted body in a freezer and it appears the body has been there for quite some time. Dexter immediately wonders if Travis has been acting alone this entire time. Upstairs we see Travis get to his feet as Dexter thinks: "Did Travis kill all those people?"