Dexter Morgan (Michael C. Hall) listens to father Harry Morgan's (James Remar) old police tape interrogations of his mother, Laura (Sage Kirkpatrick.) Laura tells Harry that a large cocaine ship will be comeing in. Harry sees this as evidence against the drug dealer, Estrada. A worried Laura wants Harry to get her out. Dexter listens in vain as he tries to make out words that Laura whispers to Harry, and grumbles that his mother is "both confidential informant and mumbler." Dexter realizes that his mother and Harry were probably having an affair, and wonders if Harry was using him the same way that he used his mother.
At NA sponsor Lila Tournay's (Jaime Murray) loft, Dexter obsesses over Harry. Lila says that it doesn't really matter, what matters is that now Dexter has an addiction. Dexter, upset, tells Lila that he built his whole life around Harry's Code. Lila admires Dexter's work - a blood spatter pattern that she has now framed and placed on a wall - and tells him that it is natural for children to have a different value system than their parents.
At the station, Sgt James Doakes (Erik King) and Debra Morgan (Jennifer Carpenter) talk about Dexter. Doakes tells Deb that Dexter is a junkie and that he goes to NA meeetings. Deb, incredulous, tells Doakes that Dexter doesn't even smoke cigarettes. Doakes fumes.
Special Agent Frank Lundy (Keith Carradine) and Vince Masuka (C.S. Lee) ride in the elevator together. Masuka worries that Lundy is tracking office computer usage and assures Lundy that he can explain some of the more questionable websites that he's been visiting. Lundy, happy to get out of the elevator and away from Masuka, announces to the station that there is a lead: the Bay Harbor Butcher has left a living victim. Lundy tells Dexter to ride along, much to Deb and Masuka's dismay.
At the crime scene, Lundy questions the alleged Bay Harbor Butcher victim while Angel Batista (David Zayas) shows Dexter where the killing almost took place - an abandoned train car. Dexter, surveying the train car, privately derides the amatuerish nature of the copycat. Lundy, reminding the alleged victim that the Bay Harbor Butcher only kills people who deserve it, asks what the victim did that was deserving of being killed. The victim admits that while he was robbing someone, the guy keeled over dead from a heart attack. Lundy, unimpressed checks the train car.
In the train car, Dexter notices that the copycat's killing tools were left behind, making him wonder if it's time for him to create a new set of standards. Lundy, out of the blue, asks Dexter if he'd use the train car location if he were going to kill someone. While Dexter notes his appreciation of the isolated location, he tells Lundy that the space doesn't support his MO. Dexter tells Lundy that the Bay Harbor Butcher is compulsive. Lundy responds that he is also predictable as well, and tells Dexter that plastic wrap was used on all the other victims, and that their copycat is likely a vigilante. Lundy casually tells Dexter about the surveillance cameras at Coral Cove. Dexter, unmoved, says that security has been needed at Coral Cove for some time.
Back at the station, Dexter asks Deb about the surveillance cameras. Deb tells Dexter that the footage captured is worthless until the station computers get upgraded so that they can replay what what captured. Deb tells Dexter that the upgrade will be completed by that evening.
Dexter and Cody (Preston Bailey) play in the sand at the beach while girlfriend Rita Bennett (Julie Benz) and her mother Gail (JoBeth Williams) look on. Dexter tells Rita that it's time for him to go meet Lila. Gail wonders about Dexter's beautiful sponsor, Lila, and suggests that they invite Lila for dinner.
That evening, Lila comes to dinner. Gail asks Lila what she is recovering from, and tells her about Rita's preference for men with heroin addiction. Lila makes light of the subject and assures everyone that Dexter is coming along well in the program. Rita is reassured. Gail wonders about Dexter's line of work as a blood spatter expert. Lila tells Gail that it makes sense, giving how Dexter's mother died. The revelation shocks Rita, who until then had no idea how Dexter's mother had died. Dexter gets up to get bread.
After dinner, Rita and Dexter make small talk. Rita tells Dexter that she likes Lila. Dexter has to leave for the office, but the two make plans to meet at Dexter's later that evening.
Gabriel (Dave Baez) and Deb have dinner and talk about Gabriel's children's books. Deb opens up about Harry and about Lundy, and confesses her jealousy over her brother being "the chosen one." Gabe teases Deb about having a crush on Lundy.
At the station, Dexter surveys the computer room. The doors are double locked, too risky for Dexter to attempt a break-in. Dexter leaves to meet Rita at his apartment.
Dexter and Rita meet up and attempt to get busy, but a phone call from Lila interrupts. The answering machine picks up, and Lila dishes the dirt about Rita and Gail. Rita pushes Dexter away to listen as Lila recalls the road trip she and Dexter took to Naples, and how she enjoyed their overnight at the hotel. Furious, Rita tells Dexter that he's just like Paul and dumps him.
The next morning, Dexter finds that life without Rita feels strange and wonders what it means.
At the station, Deb notices Dexter's funk. Dexter tells Deb that Rita broke up with him. Deb tells Dexter to fight for her because she's perfect. Dexter agrees. Deb leaves Dexter to join Lundy's morning meeting. Dexter worries that he may have missed his window of opportunity.
Streaming video of the marina plays on the computers as Lundy addresses the task force. Lundy tells the team that the vigilante advertises on Craigslist and warns that the FBI will take over the investigation if the vigilante kills anyone.
Angel interrupts, announcing that he has a suspect - Ken Olson (Silas Weir Mitchell.) Dexter contemplates erasing the computer disks and making up with Rita.
Dexter walks into his office to find Doakes listening to Harry's tapes. Furious, Dexter demands to know what Doakes is up to. Equally angry, Doakes challenges Dexter about NA and dares Dexter to hit him. Dexter leaves.
Dexter storms into Lt Maria Laguerta's (Lauren Velez's) office to file a formal complaint against Doakes. Maria tries to talk Dexter out of it. Dexter tells Maria that Doakes is obsessed with him. Maria asks Dexter, as a personal favor to her, to hold off on filing a complaint until she's had a chance to talk to Doakes. Maria orders Dexter to leave the office and take a break.
Dexter heads to Lila's loft. Agitated, he tells Lila that he's about to be found out at work. They end up in bed together. Afterwards, Dexter wonders what step in the program it was.
A calmer Dexter returns to work. Rita calls, asking to meet with Dexter to talk. Dexter agrees to meet after work. Suddenly, Dexter realizes he's "that guy" - with two women.
Maria and Doakes talk. Doakes tells Maria that he's certain Dexter is hiding something. Maria tells Doakes that his instincts have been off lately and worries he'll get kicked off the force.
Masuka and Deb share a smoke. Lundy arrives, giving Deb a disapproving look at her cigarette. Lundy asks Dexter to take fingernail scrapings of the vigilante suspect, Ken Olson.
Angel questions Ken Olson while Lundy eats animal crackers. Lundy believes that Olson is a ticking time bomb.
Dexter watches the tapes of Coral Cove and realizes that he needs to take care of things immediately. Seeing a fire alarm, he pulls it. As everyone leaves, Dexter sees his boat come up on screen. He hides under the desk until the station is empty. Dexter deletes the footage of him cleaning his boat.
Deb, upset, tells Dexter that she has to arrange protective custody for Ken Olson. She shows Dexter his file.
Later that night, Dexter breaks into Ken Olson's apartment, searching for evidence against him. Dexter finds that Olson has a wall of Bay Harbor Butcher newsclips. Olson arrives home. Dexter attacks him. Olson pleads with Dexter, telling him that they are two of a kind.
Dexter takes Olson to the train car and begins his killing ritual. He confesses to Olson that he doesn't know who he's supposed to be, and that he no longer feels the need to kill , explaining "I'm in recovery." Olson begins to feel hopeful, but Dexter, tells him that while recovery is empowering, Olson has to die so that the FBI doesn't take over the case.
Armed and ready, the task force descend upon the train car. Lundy throws the doors open, only to find it empty except for a body bag containing a neatly cut-up Ken Olson. Lundy wonders why the Bay Harbor Butcher left the body behind.
As the task force processes the crime scene, Deb finds Lundy talking on his cell phone to DC. Lundy tells Deb that the FBI won't be pulling the case, and asks her if Dexter will be in the office tomorrow. Deb worries that Lundy prefers working with Dexter over her, and laments that Dexter is always chosen over her. Lundy surprised, tells Deb that he's not choosing Dexter over her - he just can't stand Masuka. Overjoyed, Deb hugs Lundy. Realizing that she's out of line, she lets go - mortified.
Dexter and Rita talk. Dexter apologizes to her about going to Naples with Lila and for not telling her. He tells Rita about his mother's murder, and that he found the man who killed her. Rita asks Dexter if he slept with Lila while they were in Naples. Dexter answers truthfully, that they did not sleep together then, but that they slept together later. Rita kicks Dexter out, leaving him to wonder why he found it necessary to tell her the truth. Not understanding the truth-telling Dexter, he leaves Rita's house to visit Lila.