Plot

Dexter discovers that the man who murdered his mother in front of him as a boy is still alive and confronts the killer as part of his recovery from addiction - but he also discovers that old impulses die hard.

As Dexter Morgan (Michael C. Hall) waits in line to buy coffee, he listens with some satisfaction to customers as they discuss the Bay Harbor Butcher. Later, while drinking coffee with sister Debra Morgan (Jennifer Carpenter,) Dexter learns that the Marine Biologist hired by the department is still studying the algae found on the rocks used by the Bay Harbor Butcher to weigh down the body bags in the ocean. Before leaving for work, Deb tells Dexter that she'll be spending the night with her new boyfriend, Gabriel (Dave Baez.)

At a comic book store crime scene, Dexter takes samples from superhero figurines. He analyzes the blood spatter on the walls and surmises that a snow globe was the murder weapon. A poster of the Dark Defender catches his eye. He asks the murder victim's co-worker about the poster. The co-worker explains that Denny, the murder victim, was attempting to set up a graphic novel about the Dark Defender. An angry Sgt James Doakes, (Erik King,) barks at Dexter for interrupting his questioning of a potential witness.

Later, at an NA meeting, Dexter dozes off during sharing. He dreams of his mother's killers - three men with a chain saw. Suddenly, the Dark Defender appears and kills his mother's murderers. He pulls back the hood covering his face. It's Dexter as the Dark Defender. Dexter tells his mother that she's safe.

While having coffee and doughuts after the meeting, Dexter's sponsor, Lila Tournay (Jaime Murray) asks where he drifted off to. Dexter explains that his mother was murdered, and confesses that he's never told anyone his secret before. Lila suspects that his past is where his addiction began. LIla tells Dexter that he needs closure.

As Gabriel sleeps, Deb quietly goes through his things. Gabriel wakes up and sees her. Deb sheepishly tells him that she's trying to get to know him better. Deb confesses that she was the Ice Truck Killer's girlfriend. Gabriel tells Deb that he doesn't know who the Ice Truck Killer is. An angry Deb tries to leave, but Gabriel stops her, reminding her that he's been in El Salvador for the past year and knows nothing about what's been happening in Miami. Deb is relieved.

At girlfriend Rita Bennett's (Julie Benz) house, Dexter chases a wayward armadillo out of the house with a broom. Cody Bennett(Preston Bailey) and Astor Bennett (Christina Robinson) cheer. Rita's mother, Gail (JoBeth Williams) confronts Dexter privately and tells him that she knows what he is. She waves NA literature at him. Dexter confesses that he entered the program. Gail tells Dexter that if he really cared about Rita and the kids, he'd dump Rita.

At the morning briefing at the station, the results from the algae are revealed: they contain zinc and lead, narrowing down the possible harbors to only a few, Coral Cove being one of them. Special Agent Frank Lundy (Keith Carradine) and Deb take Coral Cove to investigate. Angel Batista (David Zayas) notes that Coral Cove is still affordable ona cops' salary.

Dexter reviews his mother's old files. He discovers that the last murderer is still alive, and that he was an informant. Dexter listens to one of father Harry Morgan's (James Remar) old tapes. He hears his mother telling Harry about cocaine evidence against a dealer. Harry tells her to hold out. Dexter realizes that Harry knew his mother, and that she was part of his case.

Doakes and Lt Maria Laguerta (Lauren Velez) stake out the marina. Maria tells Doakes that she is worried about him because he has had 2 shootings in less than 6 months. Doakes is unconcerned.

Lila shows up at the station to see Dexter. Angel sees her in the lobby and takes her to Dexter. Lila tells Angel that she is Dexter's decorator.

In his lab, Dexter smashes a plaster head with a snow globe. Fake blood spatters the wall, which is covered with paper. Angel delivers Lila. Dexter is clearly uncomfortable having Lila at his worksite. Angel leaves them alone.

Lila asks Dexter about his mother's killers and pushes Dexter to go talk to the last one still living. Lila and Dexter plan a trip to Naples, where his mother's killer now lives. Before leaving, Lila admires the blood spatters on the walls, and takes one of the spattered papers as a souvenir.

Deb and Lundy walk Coral Cove. Lundy stops, takes of his shoes and socks, and soaks his feet in the water. He offers Deb half of his sandwich. Deb, upset, suggests that the cross reference the rental logs among the harbors, but Lundy insists on stopping for lunch. Deb angrily reminds Lundy that they are supposed to be investigating and criticizes Lundy. Lundy tells Deb that Coral Cove is not kept up and that he wants to order 24 hour survellience on the marina. Deb, now satisfied, takes off her shoes and socks and soaks her feet.

After work, Dexter hurriedly prepares to head to Naples. Deb catches him and tells Dexter he should move his boat. Dexter waves her off.

Dexter and Lila head to Naples. Dexter tells Lila that Gail wants him to leave Rita and the kids. LIla suggests that he practice what he wants to say to his mother's killer. Dexter says that the killer stole his life, and that he's not the person he was supposed to be.

At the marina, Doakes and Maria continue their stake-out. Doakes suggests that they "pass the time like we used to," but Maria shuts him down. They argue about Doakes being fine after killing 2 people in 6 months. Angrily, Doakes confronts Maria about Bertrand, Esme's fiance. Shocked, Maria confesses that she slept with Bertand to get Esme out of the way so she could get her job back. Doakes sees the suspect. He and Maria go after him.

At the hotel in Naples, Dexter gets a call from Rita. Lila takes a shower. Dexter tells Rita that he's looking into someone from his past, and that Gail wasn't a fan of people in recovery. Rita tells Dexter that she will take care of her mother. Lila showers in front of Dexter, who is confused.

At Gabriel's apartment, Deb goes through his email while Gabriel is in the shower. She discovers that Gabriel is a writer, and that he is shopping a book called "Ice Princess." Gabriel gets out of the shower. Deb angrily confronts him and then leaves before Gabriel can explain.

Dexter walks into a bar where he immediately spots his mother's killer - the bartender (unk.) Dexter calls Lila, who is redrawing the unattractive painting over the bed in the hotel. The bartender stares at Dexter.

Rita and her mother argue about Dexter. Gail tells Rita that she's making the same mistakes all over again. Rital tells her mother that Dexter isn't leaving her. Gail goes to bed.

At seven minutes past last call, the bartender impatiently tells Dexter to finish his beer. Dexter surveys the empty bar and tells the bartender that he's visiting from Miami. He questions the bartender about living in Naples. The bartender asks Dexter what he wants. Dexter informs him that he's there to tell him how he feels. Confused, the bartender listens as Dexter tells him that he stole his life when he killed his mother. Upset and angry, the bartender takes a baseball bat out from behind the bar. Dexter tells him that he's made a big mistake and beats the bartender. Covered in the blood of his mother's killer, Dexter drags the unconscious bartender to a pool table.

Tied down and helpless, the bartender tells a frenzied Dexter that his mother had to be killed because she was a snitch and was sleeping with Harry. Just as he is about to kill the bartender, Dexter's phone rings. Lila asks if Dexter is okay. Dexter, nearly out of control, tells Lila that he is about to "use." Lila tells Dexter that he's stronger than his addiction and begs Dexter to return to the hotel. Dexter leaves the bartender and returns to Lila, who comforts him.

Back at the station, Deb reviews boat rental logs at the other two marinas. Lundy asks about Gabriel. Deb tells Lundy that they broke up. Lundy gives Deb a file on Gabriel. Deb is surpised that Lundy background checked her boyfriend. Lundy tells Deb that Gabriel is clean. Deb confesses that she went through his email and discovered that Gabriel is a writer shopping a book about her and the Ice Truck Killer. Lundy tells Deb that Gabriel writes children's books. Lundy and Deb bond. Lundy tells Deb to get Gabriel back.

Dexter wakes up to discover that he slept on Lila all night. LIla tells Dexter how she got into the program. She tells Dexter about her rage and how she burned her ex-boyfriend's house to the ground - with the boyfriend still inside. The fire was blamed on the boyfriend's drug use. Dexter tells Lila she didn't do anything wrong.

Dexter drops by Rita's house for breakfast. Rita tells him that he's part of the family and suggests that her mother will be leaving soon. To both Rita and Dexter's surprise, Gail joins them for breakfast and announces that she plans to stay in Miami - and live with Rita.

Worried about his boat and what investigators might find, Dexter decides to do a midnight cleaning. As Dexter checks for blood traces with luminol, and scrubs with bleach, surveillance cameras capture his every move.