“Tonight’s the night, and it’s going to happen, again and again — has to happen.”

That’s the innocuous way viewers were introduced to Dexter in its debut episode — a voiceover monologue that became the trademark device of the darkest storyline in the history of serial television. It wasn’t a conventional narration by any means — it advanced the plotline, of course, but it always drew us into the mind of Dexter, and forced us, against all our protestations, to actually like an undeniably demented serial killer. After all, he only killed really bad people who deserved to be chopped into little pieces and dumped in the ocean.

Season one was fraught with dark comic book humor and social satire — Dexter sent child murderers, coyotes, and murderous nurses, among others, to their just desserts, and it all seemed a bit surreal. At the same time, it was catharsis — a part of us was Dexter, and those voiceovers were our voice. We knew exactly how Dexter felt, and we loved the thrill of seeing bad guys dispatched.

What goes around comes around, and in Dexter’s case, it’s happened in spades. Season two began with Dexter unable to sleep, and his inner monologue telling us “I really need to kill ... somebody.” It’s the first hint we have that Dexter is no superhero, that he is, in fact, a very disturbed killer. That’s been the focus of this season, with his inner voice sounding more desperate than bemused.

He’s had good reason to be nervous. Once his underwater dump site was discovered, and FBI Agent Lundy’s task force started closing in on the Bay Harbor Butcher, the series has taken on a much more tense tone. It still has its humorous moments, mostly courtesy Deb and Masuka, but those are fittingly overshadowed by the twisting cat and mouse plotline.