Not all voice-overs are created equal.

Kristin Bell helps set the snarky tone of the CW’s “Gossip Girl,” and Brenda Strong adds gravitas to ABC’s “Desperate Housewives.”

But neither is asked to do what Michael C. Hall, star of Showtime’s “Dexter,” does every episode: invite viewers to listen in on the thoughts of television’s most sympathetic serial killer.

“I think (the voice-over) reinforces the sense on the part of the audience that we’re seeing things from Dexter’s point of view, that we’re in on a secret that no one else in his world is and as a result have an intimate relationship to him and are perhaps, just by continuing to watch, knowing what we know, implicated and complicit,” Hall said in a phone interview last week.

“Early on, you know, there was the thinking that I’d just record it and they’d lay it in there. And I really lobbied to take the time to rerecord all the voice-over to picture each time … It’s sort of relinquishing a little less control, or taking a little more control,” said the actor, who’s also an executive producer on the show.

Control’s an issue as well for Hall’s character, Dexter Morgan, a blood-spatter specialist who moonlights as an extremely tidy vigilante, choosing his victims according to a code laid down by his late father, Harry (James Remar), a cop who sought to give his disturbed son what he considered an acceptable outlet for his homicidal tendencies.

It’s Harry’s voice Dexter himself most often hears whispering in his ear, perhaps more often than usual this season, the show’s fourth, and so far, its highest-rated.

As Dexter wrestles with his own introduction to fatherhood, and stalks another killer — code-named “Trinity” and played by John Lithgow — who appeared at first to have managed the work-family-murder balance Harry always claimed was never possible, it may be time to ask just what kind of father Harry was, anyway.

“As with many, if not all things on ‘Dexter,’ there’s a light and a dark side to it,” he said. “The idea of a father shining a light on Dexter’s deepest darkness and telling him that he loves him, not in spite of it, but perhaps even for it, is a beautiful thing in a way. And at the same time it’s pretty twisted” that he encouraged him to kill people he thinks deserve to die.

With the Dec. 13 season finale just a few weeks away, a fifth season’s already ordered.