Dexter Morgan, blood-splatter expert for the police, drives the streets of Miami.
Mike Donovan finishes conducting a boy’s choir performance in the park. Dexter watches from his parked car as Donovan embraces his wife and children. Later, Donovan leaves in his car and Dexter garrotes him from behind. He tells Donovan to do exactly what he says and tells him to be quiet. Dexter then orders Donovan to drive to an old building in the woods. He’s dug two graves in advance and orders Donovan out. They go into the building and Dexter tells Donovan to look. Donovan refuses at first, but Dexter forces him to look at the corpses of the little boys that he killed. He explains how long it took for him to clean up the bodies. Donovan offers him anything and Dexter asks him if the boys begged. When Donovan asks him to understand, Dexter assures him that he does, but that he’d never kill children... because he has standards.
Next, Dexter strips Donovan naked and tapes him down to a table. He cuts Donovan’s cheek and takes a drop of blood, and then explains that he’ll cut Donovan apart and pack him into Hefty bags. As he places the blood drop on a slide, he says that his own part of the world will be a neater place. Once he’s done, Dexter takes his boat out and considers how his foster parents, Harry and Doris Morgan raised him.
As a child, police detective Harry Morgan confronts his adopted son and tells him that he found the grave of the neighbor dog. Dexter insists that the dog was noisy and deserved to die. Harry points out that there were a lot of other buried bones.
Dexter returns home and places Donovan’s slide in a hidden case along with several others. Satisfied that he has fulfilled the Code of Harry, Dexter remembers how Harry taught him to cover his tracks and think like a police detective. He checks his answering machine and finds a message from his adopted sister, Debra, asking him to come to a crime scene.
Dexter goes to the motel crime scene and finds his sister Debra, a police officer, dressed as a hooker from an undercover vice operation. She explains that they found another hooker dead in the empty pool, chopped up in pieces. The officer in charge, Lt. Maria LaGuerta, refuses to let Debra on the case. Dexter tells his sister that she should learn some politicking skills from LaGuerta, but Debra just wants to catch the serial killer and get out of Vice and into Homicide. She wants Dexter to provide any hunches and brainstorm with her, and he reluctantly agrees. While he looks at the crime scene, he tells her to avoid LaGuerta and talk to Captain Matthews, an old friend of their father who could put her on the case.
Dexter talks to the forensic experts handling the case, Vince Masuka and Angel Batista. Vince wonders why Dexter is there, noting that there’s no blood. Dexter is impressed that the killer was able to cut apart the hooker’s body without leaving any blood. There are no prints, but Angel notes that the killer didn’t finish the job this time. One of the incisions is incomplete, and they figure he was interrupted. As Dexter leaves, LaGuerta winks at him and he admits to himself that he doesn’t understand human mating rituals at all. He is impressed that the killer may have exceeded his own abilities.
The next day, Dexter brings doughnuts to work and chats with his co-workers. Debra comes by and informs her brother that Matthews put her on the case over LaGuerta’s objections. He congratulates her and she asks him for his ideas, but Dexter tells her that he hasn’t considered it yet. He then goes to see the records supervisor, Camilla, to get the records and flirt with her.
Back in his office, Dexter is considering blood splatter patterns when Sgt. Doakes demands a report on a medical case. Doakes is unimpressed by Dexter’s genial demeanor and demands an analysis.
Dexter goes to Doakes’ crime scene and explains the patterns to the cop on duty, Simon. Once he’s done, Dexter gets something to eat and checks out Jamie Jaworski, a hotel valet who he believes killed Jane Saunders, a wife who disappeared. Jaworski’s lawyer got him off on a faulty search warrant. Dexter breaks into Jaworski’s home and avoids the man’s dog. He then finds Jaworski’s video camera and porn magazines, and realizes that Jaworski’s need for violence sex is evolving.
Harry talks to Young Dexter, who admits that he’s considered killing people instead of dogs, but figures that his adopted parents wouldn’t like it.
Friday night is date night in Miami, and Dexter visits the woman he’s chosen so he can pretend to have a girlfriend. He goes to the home of the woman, Rita, who he’s been dating for the last six months. The victim of domestic abuse, she’s as damaged as Dexter in her own way. Since her former husband raped her repeatedly, she has no interest in sex, just like Dexter. While he waits for her to get ready, he talks to Rita’s two children, Cody and Astor, who clearly like him and vice versa. Dexter and Rita go out on the pier, and Dexter notices the police gathering at a murder scene. He goes over to investigate and finds another dead and bloodless hooker, cut up into pieces. Angel is there and impressed that Dexter as on a date. He explains that there are small differences in the cuts, differences suggesting that he’s experimenting. This time the killer took the head.
Dexter drives Rita home while expressing his admiration for the killer. He tries to touch her thigh but Rita says she doesn’t want to and removes his hand, saying she isn’t ready. Dexter has no idea what he’s done wrong, and can’t get the image of the bloodless body out of his head. At home, he checks out one of Jaworski’s S&M websites and finds a video of a shadowy man raping the dead wife. The video shows a tattoo that matches the one that Jaworski has, confirming his guilt. However, he has to wait until the proper time to follow the Code of Harry.
Harry comes to see a teenage Dexter and accuses him of going behind his back with his “urges.” He shows his adopted son the bloody knives that he found, and Teenage Dexter insists he only kills animals. Harry figures that what happened to Dexter’s birth parents got into him and twisted him. He believes that Dexter is at heart at a good kid, and that if they can’t stop his urges then they can channel it and use it for good. Harry wants him to go after the terrible people out there that the police can’t catch, the people who deserve to die. He plans to teach Dexter how to spot killers and cover his tracks, and assures Dexter that he can make the best of his urges and that he is loved.
Dexter ritualistically goes over his plans to kill Jaworski, preparing an abandoned building in advance and lining it with duct tape and plastic sheets.
Dexter meets with Debra and suggests that the hooker killer ritual’s is changing as he looks for inspiration. She asks him about his date with Rita and says she needs a guy she can trust. When Dexter jokingly says that he’d like to talk about children instead of murders, Debra accuses him of sounding like their mom. She asks him about cell crystallization, and explains that she overhead that the coroner determined that the corpse was frozen. He realizes that cold slows the flow of blood and figures that it’s important, but Debra wants more. Dexter tells her that the killer is using a stolen refrigerated truck to slow the flow of blood and dump the body afterward.
As Dexter returns to police headquarters to attend LaGuerta’s briefing on the serial killer, he overhears Mrs. Donovan making a report about her missing husband. Doakes approaches Dexter and wonders why he cares about the woman. He complains to LaGuerta that Dexter shouldn’t be part of the briefing, but she agrees to let him in. He sits down next to Debra and tells her to make her case. When LaGuerta asks for reports, Debra they look for a stolen refrigerated truck. Debra stumbles through her presentation but LaGuerta dismisses her idea and tells them to concentrate on the witness who must have interrupted the killer. Afterward, Dexter tells her to find the truck on her own. LaGuerta comes in to call Dexter to her office. Debra figures that Dexter is having sex with her and walks away.
Dexter meets with LaGuerta and Doakes and insists that the murder was a crime of passion, not a drug deal gone bad. He suggests they look for an ex-boyfriend and LaGuerta agrees. Before he goes, Doakes warns Dexter that he’ll be watching him.
That night, Dexter follows Jaworski to a construction site where he steals copper pipes. He hangs up a photo of Jane and lures Jaworski over so he can see it, and then injects him with a paralytic. After stripping him and taping him down, Dexter asks him to confess. Jaworski readily does so and Dexter kills him and cuts him apart. As Dexter finishes up, his cell phone rings. It’s Rita, who apologizes for the other night and asks him to come by. Dexter says he’s finishing up a project and promises to come by later.
As Dexter drives to Jaworski’s hotel, a refrigerated truck drives by him. He follows it toward the Port of Miami and watches as it stops on the bridge, turns, and comes back toward Dexter. The driver tosses the hooker’s missing head onto Dexter’s windshield and keeps going. Dexter calls in the police and LaGuerta goes over his story. She’s skeptical of his story that he just happened to bump into the refrigerated truck, and the driver just happened to have the head with him. LaGuerta flirts with him and admits that Dexter’s theory about the drug killing was correct. When she draws closer to him, Dexter quickly backs away.
As the sun come sup, Dexter goes to see Rita. She was worried when he didn’t show and called in sick, and asks if he’s okay. Dexter explains that there was another hooker murder, and Rita tells him that the kids are sleeping next door. She invites him in Dexter accepts. Rita then says that she wants him and removes her robe. Dexter thanks her and she kisses him. They get onto the couch but before they can proceed, her phone rings. It’s Cody, who wants Rita to come get him. She agrees and tells Dexter that Cody threw up. Before she goes, she asks Dexter if everything is okay. He assures her that they’re better than okay and tells her to be a good mom. Once Rita leaves, Dexter sighs in relief.
Back home, Dexter figures that he has to keep a lid on sex with Rita or it could ruin their relationship. As he enters the kitchen, he finds a doll’s head glued to the refrigerator door. Inside is a doll, cut into pieces just like the hookers. One hand is holding a doll’s mirror. Dexter figures that it’s a friendly message from the killer inviting him to play... and he’s eager to accept.