“Dexter”
Sundays, 9 p.m.
Showtime

“Californication”
Sundays, 10 p.m.
Showtime

“Most actors toil in obscurity, never stepping into the spotlight,” Michael C. Hall says as episode four in the new season of “Dexter” ends. “But if you hone your craft, work diligently, you might just find yourself cast in the role of a lifetime.”

Hall is talking about something experienced by his character, a police forensics expert who also happens to be a serial killer. But he may as well be spinning a metaphor for what he and David Duchovny are experiencing on their respective Showtime series.

It’s true that both actors already have spent significant time in the spotlight — Hall in “Six Feet Under,” Duchovny in “The X-Files.” Yet here they are, carving out new and exquisite territory in a one-two punch of programming that’s as good as any channel on television.

Hall begins his third season as Dexter with the usual intoxicating dead stare of a man who can kill without emotion. But this time, he must deal with a wholly new problem: While trying to exact revenge on a drug dealer who got away with slaying two teenage girls, he kills someone he didn’t know, someone who’s connected to a politically powerful family.

Meanwhile, Dexter finds himself with a friend (played with a bit of off-balance splendor by the usually stoic Jimmy Smits), Dexter’s girlfriend Rita (Julie Benz) delivers some shocking news and his sister Debra (Jennifer Carpenter), who’s also a cop, is gunning hard for her detective’s shield.

Hall wanders through these scenarios beautifully, like a man watching a movie of his own life and not quite recognizing what he sees. Dexter lives inside his own head most of the time, even when he’s with family and colleagues. With Smits, he adds a new layer of insecurity to the mix.

Underneath it all, “Dexter” is a police procedural drama, a whodunit and how’d-they-do-it not unlike “CSI” and so many other series. But you don’t even think about that when you’re watching; instead, you’re always on the lookout for what the characters are going to do, say and think next. That’s a mark of brilliant drama, which “Dexter” is.

“Californication,” on the other hand, is a tragedy played like a laugh-track-free sitcom. When we last left this world, at the end of season one, Duchovny’s character, writer Hank Moody, had just gotten what he wanted. That is, the love of his life, Karen (Natascha McElhone), left her husband of a few hours and ran off with Hank and their daughter, Becca (Madeleine Martin).

Now what?

Well, there’s accidental cunnilingus (trust me, it makes sense), a short jail stint, a chance encounter with an old acquaintance who’s a hooker, an unexpected pregnancy, an opportunity for Hank to write the autobiography of a crazed, wildly successful record producer and one of the funniest, most cringe-worthy dinner parties you’ll ever eavesdrop on.

Hank claims to want peaceful domesticity with Karen and Becca, but he’s one of those people that trouble just seems to find. But he accepts his descent with a smile so disarming that most of those people around him don’t mind joining him for the ride down.

Judging from the first four episodes, season two is just as much sly fun as its predecessor as it mocks California excesses. And Duchovny is an absolutely charming reprobate, drinking, fighting and screwing his way through life. He manages to make his inevitable decline look attractive.

Both “Dexter” and “Californication” offer the added bonus of excellent supporting casts. Carpenter’s tough-talking Debra is nasty-sexy, and ex-“Oz” actors Lauren Velez and David Zayas both bring brains and toughness to their roles as the superior officers in the Miami Metro Homicide division.

“Californication” gets extra juice from McElhone, who blends love and suffering so well, Evan Handler, who plays Hank’s manager, Charlie Runkle, and Pamela Adlon (Marcy Runkle). They come to season two with a whole new bunch of addictions, obsessions and complications. Great roles all.

So let that be a lesson to you actors out there: Hone your craft, work diligently and you might get the role of a lifetime. Maybe even two.