With Debra recovering in the hospital, Dexter re-doubles his efforts to locate the Trinity Killer. Knowing that he is following the same pattern as his murders from 30 years ago, Dexter is sure he knows where he will strike next. Afterward, he follows the serial killer to his home and is shocked by what he finds. Dexter also has some explaining to do when Rita finds out that he never gave up his apartment and still keeps some of his possessions there. Sgt. Batista plants a news item about the suspected Vacation Murderer that bears fruit. Having told her superiors of her relationship with Batista, the Deputy Chief delivers some bad news to Laguerta.
Dexter visits Debra in the hospital where she is recovering. When Anton arrives, Debra tells the truth about Lundy to him and calls off their relationship. The police believe that Lundy and Debra were shot by the Vacation Murderer, but Dexter is sure that Trinity is the responsible for the crime. Rita receives a phone call from Dexter's landlord and she finds that Dexter has kept his apartment. Angel plants the information with Christine that Johnny Rose has syphilis and Nikki Wald guns down her partner, Maria discloses her relationship to her superiors and Angel is promoted and transferred to another precinct. Debra has a nervous breakdown. Dexter chases Trinity and makes an unexpected discovery.
Recent events spur Dexter into his own investigation of the Trinity Killer.
- Dexter arrives at the scene of Debra and Lundy's shooting. Angel tells him that Debra is alive, but Lundy has been killed. They think Debra will be okay, and the shooting looks like the work of the one the media have dubbed the "vacation murderer." Dexter realizes that Debra was "with" Lundy. Dexter thinks it is strange that Lundy was shot twice, but the shooter passed on the opportunity to finish-off Debra.
Christine gets to the scene claiming to be concerned about Quinn. After thinking for a second, Angel goes on the record with Christine and says they believe "vacation murderer" suspect Johnny Rose has an untreatable case of syphilis.
Dexter talks with Harry in Lundy's hotel room. Dexter thinks the shooting may have been the work of Trinity and begins taking pictures of Lundy's research and collecting his audio notes.
We see Trinity watching a news report at a diner. He's particularly upset his omelet was not prepared the right way and gives the counter girl a nasty time about it.
Rita gets a call at home from Dexter's landlord that there is something wrong at Dexter's apartment.
Debra wakes up in the hospital. Dexter asks her about the shooting but she doesn't have any helpful memories of the incident. Anton comes in the room and Dexter gives them some privacy.
In the hospital hallway Rita references Dexter lying to her about getting rid of the apartment.
Debra admits to Anton that she slept with Lundy. He offers to stick around until she recovers, but she tells him he deserves better and they break up.
Maria admits to Angel she disclosed their relationship to the brass. Angel is furious that she made the decision without consulting him.
Without many leads on Rose, Angel tells the guys his plan for releasing Rose's syphilis. The hope is that since his girlfriend does not have the disease, she will turn on him for cheating.
Dexter goes to his apartment and begins to work through Lundy's notes on Trinity. Debra calls to say she is being released and needs to crash with Dexter and Rita. Dexter learns how close Lundy felt he was getting to Trinity, and that the killer is obsessed with ritual. Harry is adamant Dexter needs to kill Trinity.
Trinity buys a new hammer in order to "finish what I started."
Rose's girlfriend spots her face in the newspaper and the headline stating that Rose has an STD.
Dexter sees that Trinity will next bludgeon a man with two kids in an apartment building. He realizes that Lundy's most recent notes are on the recorder locked in evidence.
Quinn shows up and gives Christine a sexual present for her writing the article. He seems to be into her again.
Debra arrives at Dexter's place. Rita tries to discuss Dexter's apartment lie but he asks her to wait.
Angel didn't spend the previous night at Maria's. She apologizes and he seems cool with it.
Dexter on a pretext gets into the police evidence room and obtains Lundy's latest tape from his pocket recorder.
Trinity pretends to be interested in an apartment in the building and has a security guard (who has kids) give him a tour. They get a cup of coffee and Trinity acquires a good bit of info about the guard and his evening schedule.
After Dexter leaves, Rita asks Debra if she knew about the apartment. Debra had no idea, and tells Rita she feels responsible for Lundy's death.
Dexter listens to Lundy's tape and get a physical description of Trinity.
Rose is found dead with three bullets in his chest. Rose's girlfriend is cornered in a nearby alley, pacing around with a gun and methed out of her gourd. While other police attempt to get her to comply with verbal commands, Quinn finally tasers her and they bring her into custody.
Quinn excitedly calls Debra to tell her they have the shooter.
Maria is informed by the boss that she must transfer Angel out of homicide.
On his way to get Trinity, Debra has Dexter meet her at the shooting site. She yells at him about the apartment. Debra is beside herself with grief, convinced that she is a "broken" person.
Rita is waiting for Dexter in his apartment. He shows her that all he has locked up in his chest is Harry's old shotgun, but Rita is disturbed by how well is able to lie and says the marriage needs "a lot of work."
Later that night Trinity is inside the building when Dexter pulls up. Dexter goes in but finds the security guard is walking around unharmed. The victim is the coffee shop guy, and Trinity proceeds bash him in the skull with the new hammer.
Dexter isn't able to get to Trinity before the killer leaves the building, and is forced to follow him in his car. He is surprised to see Trinity drive to the suburbs and pull into a nice family home.
"He doesn't belong here," Dexter tells the omnipresent Harry. "It doesn't make sense."
Dexter sneaks towards the house with hypodermic in hand only to watch stunned as Trinity walks in the door and is greeted by his wife and kids.
"Lundy was wrong, I was wrong," Dexter thinks to himself. "None of us knew pieces of the puzzle were missing. Trinity's a husband, a father. He's like me."