When a local convict claims he has new information regarding a fifteen-year-old crime spree, Miami Metro sets out to unearth new evidence on the case. Debra attempts to cure Dexter of his killer tendencies. Meanwhile, the Mike Anderson Murder Case leads to the Ukrainian Mob and a vengeful Louis Greene won't stop meddling with Dexter's life.
Dexter is trying to calm Debra down following his second "big reveal," that he is a serial killer. He tells her that he's been killing since he was twenty and only kills certain kinds of people. Dexter explains his dark passenger and his code. Even knowing the type of people Dexter kills, Debra isn't sure what to do. She punches Dexter in the face and storms out.
At the office, Debra looks up The Bay Harbor Butcher. She also reads that serial killers have a type of addiction and will continue to kill until caught.
Since Debra found the prosthetic hand in his apartment, Dexter realizes it can't still be in evidence. While he looks, a panicky Vince Masuka walks in and tells him about the hand being stolen. Masuka says he put Louis in charge of finding it. He's relieved when Dexter says he's not going to turn him in.
At Debra's next briefing, the plan is to shut down the strip club twice a day until somebody tells them something about what happened to Mike Anderson. Debra tells them a murderer named Wayne Randall (who went on a multi-state killing spree with his girlfriend) now says he has evidence of an additional victim and wants to lead authorities there to clear his conscience. Dexter volunteers for the job, but Debra assigns Vince Masuka.
Outside the station, Debra tells Dexter she came very close to arresting him, but doesn't know what to do. Her plan is to conduct a kind of rehab for Dexter, which basically consists of him moving in and her watching him 24 hours a day.
Maria LaGuerta hears back from a private lab that the blood on the slide found in the church belonged to Travis. She instructs the person to keep everything very hush-hush and calls the FBI.
The guys shut down the strip club yet again and manager George Novikov is getting upset. Quinn hits it off with a dancer, Nadia. She gives him the name of Kaja's bouncer boyfriend, Tony Rush, (who didn't show up for work) and he leaves his card.
On the first night of serial killer rehab, Debra instructs Dexter he'll be sleeping in her bed, while she sleeps on the couch. During spaghetti dinner, Dexter says his need to kill starts with seeing blood, which eventually turns black. That night, Dexter begins to research the plans of Louis Greene's penthouse.
Masuka complains about the Randall case being mostly waiting around while the diggers try to find the body. Dexter volunteers to relieve him, but he needs Debra's permission. She's all set to go with him until Angel shows up with the info about Viktor, who is a member of Ukrainian organized crime.
While waiting at the dig site Dexter strikes up a conversation with Randall. Dexter asks about his change of heart. Randall says he decided to "surrender."
Dexter sneaks to Louis' penthouse during lunch. While he's there, he learns that Louis was the one who cancelled his credit cards. On the computer, he finds several videos, one with Louis and a prostitute. He finds evidence that Louis probably framed a man in order to take control of his software company. Louis comes home unexpectedly. He sees his laptop open and Dexter pins him up against a wall, demanding to know why he's screwing with him. Louis says it's because Dexter trashed his video game, Homicidal Tendencies. Dexter says he never wants to see him again, either at work or with Jamie.
Back at the site, Debra is upset Dexter is running late. Randall notices the dispute and Dexter tells him about the boss/sibling dynamic. He asks Randall for clarification on the surrender line and he says once he stopped fighting it the anger went away.
After yet another strip club shutdown, George goes back to his office to find Isaak Sirko. Isaak clearly runs the organization and George is surprised he's in the U.S. Isaac believes George when he says he knows nothing about Viktor's disappearance.
Dexter comes home and is surprised to see Louis there, hanging out with Jamie Batista, flaunting the fact he's not scared of Dexter. Dexter thinks to himself that he needs to stop Louis.
After the ride home, Nadia flirts with Quinn without giving him more information.
Dexter injects drugs into Debra's steak that night so he can sneak into Louis' place. He sneaks up behind Louis and knocks him out with a needle. Dexter takes Louis to a location, then seems to have second thoughts. He calls Debra and tells her he's seeing the blood. She arrives and he tells her that he couldn't go through with it. She thinks he took a major step by calling her. After Debra leaves, Dexter simply leaves Louis on a park bench.
Isaac and Jurg Yeliashkevych pay Tony a visit. After tricking Tony into admitting that he spoke with the police, Isaac sticks a screwdriver into his right eye socket, killing him instantly.
The next day, Dexter and Debra are back at the Randall dig. When Debra goes to grab some ice cream, Randall talks about the fact he never got to patch things up with Hannah, the girlfriend with whom he committed his murders. He says Hannah only sees him as a killer. Randall says the clock has run out, then runs onto the highway in front of a large truck.
- This Episode was previously titled "The Shadow Knows" however it received a title change to "Sunshine and Frosty Swirl." This is the first of two episodes to have its name changed in Season Seven, the second being The Dark... Whatever (formerly known as "Because I Want To").
- In this episode, Dexter tells Deb that he's been killing since age 20. Later, in "Dress Code", Dexter tells Dr. Vogel that he first killed at age 19.
- Bay Harbor Butcher Case
- Blood Slide Boxes
- Code of Harry
- Debra's Beach House
- Dexter's Apartment
- The Fox Hole
- Frosty Swirl
- Homicidal Tendencies (Louis Greene's video game)
- Kill Tools
- Koshka Brotherhood
- Louis Greene's Penthouse
- Mike Anderson Murder Case
- Prosthetic Hand