With the help of his newfound friend Brother Sam, Dexter wonders if there is light within him to counter the darkness, while the search for the Doomsday Killers takes him in a new direction; Batista and Quinn pay a visit to the university where Professor Gellar taught; due to departmental regulations following the shooting, Debra is forced to begin therapy.
While Dexter is examining the angel wings from the last staged murder, he's thinking that the man he saw in the crowd might be involved. He finds that the wings have been repaired with an unusual glue.
Elsewhere, Travis and Gellar are talking about needing to hunt again, but they need to find a "whore of Babylon" for their next Book of Revelations scenario.
Dexter learns that the glue from the wings is something used in ancient manuscript repair.
During Deb's briefing we learn that the dead woman worked at a Miami cultural center cafe. Detective Anderson has done more research on Revelations. The victim recently had sex. They are looking at a former assistant of Gellar's named Charisa Porter. Another number, 1244, was in the victim's esophagus. Masuka's new intern, Louis Green, has discovered the most repeated number in Revelations is1260 and the guess is that they might only have a few weeks. Dexter doesn't reveal to Deb what he's found.
Masuka asks computer wiz Louis to help him with his missing evidence problem. He wants to get the Ice Truck Killer severed hand previous assistant Ryan stole, back from the on-line purchaser.
Quinn asks Deb, who had completely forgotten that she still had it, for his engagement ring back. After he leaves she calls Jamie and asks her to look around the apartment for the ring she's misplaced.
Sam drops by the station to report his garage having been shot up. Dexter invites him to drop by and see Harrison.
Dexter goes to the museum following a restoration glue clue. He spots Travis in an instructional video.
Anderson calls Dexter to a double homicide scene. Within minutes Dexter is able to figure out that what occurred was actually a murder-suicide. Anderson is impressed.
Travis and Gellar are at a nightclub scouting for their next victim. They see Gellar's face on the front of the newspaper in connection with the Doomsday killings and decide Travis should find the next victim on his own.
Dexter finds Travis's name on the museum's website. He researches his name and finds out Travis has no record. Sam drops by and hangs out with Dexter. Dexter reveals to Sam that witnessing his mother's death at age 3 is what created the darkness inside him that drew him to work in homicide. Sam thinks that Dexter could use the power of good to get past his darkness.
Travis makes an awkward and thoroughly inept attempt to abduct a young woman leaving a party and fails. Travis reports his failure to Gellar, who says he'll need to assist.
When Travis leaves his house Dexter breaks in to look for evidence of his involvement in the murders. He finds that the page numbers in Travis' bible have been cut out. Dexter carefully excises one of those pages. It ends up being a perfect match for one of the numbers found on one of the victim's bodies.
Quinn and Angel interview Porter. She had a brief relationship with Gellar and doesn't think he could possibly be involved. Quinn asks for help while spending their night on the road and she offers to meet them.
Anderson tells Deb about his murder-suicide and her brother's acumen at the scene.
Quinn and Porter hit it off and start getting drunk together at a bar as Angel leaves, disgruntled. They end up hooking up back at her place for the night.
Deb is doing work at Dexter's place surrounded by crime scene photos. When Harrison comes in to give her a hug goodnight he walks right into the graphic photos. Jamie is furious and this starts a fight between the nanny and the aunt. Dexter comes home and remains neutral, but tells Deb that perhaps she needed to be more careful.
Gellar puts his foot on the gas and forces Travis to drive his car into a young couple. Travis grabs the woman and sticks her in the trunk.
The next morning Angel stops by Porter's place to get Quinn. While waiting for Quinn he goes through a box labeled "Gellar" and finds a journal in which are sketches depicting an angel-themed murder exactly like the one that recently happened. Porter confirms Gellar drew the sketches.
Deb goes to see a counselor and gets some stuff off her chest. Soon after she goes to the house where Anderson's murder-suicide took place and gets the guy to rent the place to her at a reduced rate.
Deb has her engagement ring back, and sticks it in Quinn's desk drawer.
Louis has come up huge for Masuka. He couldn't find the name of the person who bought the hand stolen from the evidence locker, but he was able to erase any record of the sale from the Internet auction site. He also cleans up Vince's browser history, including any visits to favorite porn sites. Masuka gulps quietly and bears it.
Dexter is waiting for Travis in the back of his car, and loops a garrote around his throat and applies enough pressure to control the man. He has him drive a few blocks and asks him about the murders. Travis says that Gellar does the work of God and seems angry that he has been too weak to actually commit any of the murders himself. Dexter ends up dropping him off.
Travis calls Gellar and tells him he isn't feeling well. Gellar seems to know something is up.
The next day Dexter watches from up the street as Travis gets into his car.
We then see Sam opening his garage for the day only to be gunned down by an unseen shooter who had been waiting for him.