'Dexter': Deb tells her brother she's in love with him

Last night's episode, "Argentina," will go down as the one in which Deb (Jennifer Carpenter) revealed her incestuous feelings to her foster brother, Dexter (Michael C. Hall). These were uncovered last season during sessions with Deb's shrink, causing a rare unification of all America behind a single cause: Please don't go there, "Dexter" producers.

After eight episodes in which this uncomfortable twist seems to have been forgotten, Deb returns to it as she reaches her snapping point over Hannah McKay (Yvonne Strahovski). Before she is even aware that Dexter is having a love affair with her prime suspect, Deb plays him the interview Price conducted in which Hannah admitted stabbing one of her victims. Deb implores Dexter to kill her, noting how well she fits his code. But Dexter refuses, telling her that he just can't do anything that she couldn't live with later. ("It turns out there’s a (expletive) of a lot that I can live with these days," Deb replies.)

Of course, Dexter's not coming clean. He won't kill Hannah because he's in love with her. To him, the relationship -- in which all aspects of himself are accepted -- feels more like home than his own home. Slowly, he lets his guard down around his fellow serial killer. He hadn't mentioned until now that his sister was the lieutenant threatening to end her freedom, for instance. He also neglected to mention the existence of his son or stepdaughters. When Hannah sees Dexter playing with the children, she wonders whether he was afraid the information would have pushed her away, or if he just didn't trust her. (It's a little of both.)

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Meantime, Dexter goes to get a doughnut and nearly gets killed by Isaak Sirko (Ray Stevenson) instead. He bends over to grab his dropped keys just as Sirko fires from the street.

Next, it's Dexter's turn. He breaks into Sirko's house, planning to leave his corpse and let the police blame it on the Colombians. Instead, he finds another assassin already there, waiting to do the same.  He was hired by the Koshkas on the advice of club manager George Novikov (Jason Gedrick), who ratted out Sirko for his unbusinesslike vendetta against an employee of Miami Metro.

Instead of agreeing to go halfsies on the kill, the assassin fires at Dexter, who returns the favor by slitting the dude's carotid artery. Later, Sirko finds the dead Koshka and remarks: "So much for brotherhood." He calls the police to investigate the homicide committed by the blood spatter analyst who walks in with the police. ("My my," he tells Dexter. "You couldn’t have described it better if you’d have been there yourself.")

Later, Dexter tracks Sirko to a bar. But instead of another victim, he gets some unexpected answers. It's a gay bar, and Viktor was much more than a friend, it turns out, which explains Sirko's vendetta.

"You took from me the one thing that money and power can’t bring back," Sirko tells Dexter, likening Viktor to Rita. Dexter disagrees. Viktor was a killer who deserved to die; Rita an innocent victim. Sirko responds that love blinds everyone to such distinctions. They agree to fight another day -- presumably because Sirko has identified Dexter by name to their bartender.

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In a subplot sure to balloon in coming episodes, LaGuerta (Lauren Velez) launches her investigation into Dexter as a potential Bay Harbor Butcher suspect. She discovers both his boat and a former marina worker who noted how strange it was that he abandoned his former slip with eight months left on the lease.

And Quinn (Desmond Harrington) is trapped more tightly than ever under the Koshka thumb. Novikov has some drugs to move and wants a cop around to make sure the deal goes down safely. So he pays a visit to Quinn, carrying a tape of a phone call in which the detective is heard promising to steal police evidence if Nadia (Katia Winter) is freed.

Still, nothing in this episode has as much resonance as the exchange that begins when Deb spots the keys to Hannah's car, which Dex borrowed to evade and stalk Sirko. Deb implores Dexter to stop seeing Hannah, to think about what happened to her husband.

"Are you in love with her?" she asks. "Is it because she’s a serial killer? Does that turn you on or something? Do you sit around and talk about who you’re going to take out next?"

Dexter replies: "I feel like if you love me, you’ll accept this."

And that's when it happens.

"If I love you?" Deb asks. "I went to the church that night you killed Travis Marshall to tell you I was in love with you."

Yikes. It's hard to imagine a close second to the shock of telling your cop sister that you're a serial killer, but this reveal has achieved it. Dexter sits down to absorb what he's just heard, appearing not to know how.

"It’s one thing to be in love with your brother," Deb says. "But it’s a whole other level to be in love with your brother who’s a goddamn (expletive) serial killer."

Deb follows this observation up with probably the best single "Dexter" quote ever: "You’re a serial killer and I’m more (expletive) up than you are."

Dexter can only respond: "I’m sorry. I don’t know what to say."

One thing's for sure: Thanksgiving with the Morgans will be awkward this year.

"Dexter" airs Sunday nights at 9 p.m. ET/PT on Showtime.