Sergei Bachlakov, The CW
Jensen Ackles stars as Dean and Jared Padalecki stars as his brother, Sam, in "Supernatural."

"Supernatural" returns on Thursday for its fourth season, and it's still one of the best shows-you're-not-watching on TV.

Three cheers for The CW for renewing it despite its, um, ratings challenges.

The supernatural thriller is smart, scary and exceptionally well written. In the Grand Pantheon of Television, it deserves a spot right up there next to "Buffy the Vampire Slayer."

And, beginning Thursday (8 p.m., Ch. 30), "Super-

natural" does something for the second time that few shows are capable of doing successfully even once. It reinvents itself.

Don't get me wrong. It's still about the Sam (Jared Padalecki) and Dean Winchester (Jensen Ackles) hunting down demons and other evil beings. But, for the second time in as many seasons, the show has headed in a different direction.

When "Supernatural" began, Sam, Dean and their father, John (Jeffrey Dean Morgan) — whose whereabouts were unclear — were hunting for the demon who killed their mother/wife. Along the way, the brothers took on a variety of creatures out of folk tales but always moved in the direction of destroying the Yellow-Eyed Demon.

But, unlike some other shows (like, say, "The X-Files"), "Supernatural" didn't try to drag that out forever. After two seasons and 44 episodes, creator/executive producer Eric Kripke and his team neatly wrapped up that storyline and killed the Yellow-Eyed Demon.

But, in the process, a whole lot of other demons were unleashed from hell, which led to last season's redirection. The Winchester brothers had to start hunting them down.

And, at the end of last season, Dean was sent to hell ... which is one, um, heck of a cliffhanger.

When Season 4 begins, it doesn't take long for Dean to return from hell. Although it does take a while for him to figure out how that happened.

I'm reluctant to tell you much more for fear of giving anything away. Because the first couple of episodes are full of some great surprises. Shocking turns of events, even.

(As always, the show is plenty gross and violent. But, compared to theatrical horror movies, it remains rather tame.)

It's not like the narrative has forgotten what happened before. The fourth season builds on the first three.

But there are some huge changes that make for a great new start.

(Although, even if you've never seen the show before, you can quickly pick up on what's happening.)

Reconfiguring an ongoing season is one of the hardest tasks in television. If you don't think so, just looked at Fox's abysmal "Prison Break," which is also in its fourth season.

The producers/writers have revamped the show three times, and each season has been worse than the one before. Currently, the only reason to even tune in to "Prison Break" is to laugh at how ludicrous it has become.

Unless you think killing a character, cutting off her head and then bringing her back on the show is anything other than funny.

Fans of "Supernatural," on the other hand, have another great season of that show to look forward to.

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