This week on Supernatural: demons, humans, hookers, and theological musings about the nature of good and evil. Episode 3x04, "Sin City," opens with a scary scene that doesn't appear to be supernatural. A man shoots himself against a cheerfully colored stained-glass window in a church. (Remember what I said before about bright colors on Supernatural? They're trouble, I tell you.)

When we first see the Winchesters, Dean (Jensen Ackles) and the Winchester's adorably caustic substitute father figure Bobby Singer (Jim Beaver) have dismantled the antique Colt revolver. Sam (Jared Padalecki) has gotten wind of demonic omens and the suicide, so the boys go off to investigate while Bobby keeps working on the Colt. According to the local priest (Robert Curtis Brown), the factory town has recently turned into a den of debauchery. Sam and Dean head off to a bar that's the hotspot of the town's night life, where there's a lot of booze and scantily clad hookers. Dean saves a man from shooting himself. What is supernatural here is may still be a question mark, but Dean still gets to be the hero.

At their hotel, Sam and Dean met another hunter, Richie (Martin A. Papazian), someone Dean knew while Sam was in college. We get down to demons when Richie (who Dean describes as "a sweet moron") accompanies the bartender, Casey (Sasha Barrese), to her cellar hideaway. Instead of getting a night of kinky bliss, Richie dies in typically gruesome style when Casey reveals herself as a demon and turns his head around. Literally. Yikes. Also, how sad is it that we find out Dean had a hunting buddy and then the guy dies?

Meanwhile, Bobby is testing the Colt when Ruby, the show's current resident demon, shows up. In a snarky style typical of all Supernatural's demons, she challenges Bobby to shoot her. Bobby -- who seems a lot more ruthless than he was at the end of season 1 -- does so. Ruby, mildly irked by being shot point blank in the chest, offers to help Bobby fix the gun. Katie Cassidy seems comfortable in her role, and continues to be interesting to watch, although the Kristin Bell impression is distracting. I think Cassidy does have the capability to own the role and make Ruby a truly interesting character.

Dean tracks Richie's last location, and goes with the bartender to her lair, where Dean's already prepared a devil's trap. The caught demon in turn causes a minor earthquake, trapping Dean, who loses his book and can't recite the exorcism ritual from memory. That's plot convenience but also consistent with what we know of the Winchesters' experience with exorcisms. (Memo to Sam and Dean: you are at war with demonkind. Please memorize things.)

Sasha Barrese turns in a sophisticated, likeable performance as Casey. It turns out the deaths in town weren't directly from supernatural causes, but by-products of the slide into vice. All the demon did was make a suggestion to a greedy business owner, Trotter (Don Davis). She unspools a demon's perspective on hell and humans to Dean. "I don't see that you and your God have done such a bang-up job. War? Genocide? It's only getting worse." Casey reveals the Yellow Eyed Demon's name, Azazel. She also says that Lucifer is slated to make a return, and that without Sam taking up his role as leader of the demon army, it's chaos. There's a lot of exposition here, but it's juicy, chock full of mytharc fun facts and broader issues.

Dean asks Casey what hell is like. When she asks him if he's scared to go there, he denies it. And there, finally, is the first true crack in Dean's armor this season. Jensen Ackles does more with a few moments of stillness than some actors can do with a page of dialogue. We see the stifled fear behind Dean's eyes. Dean's conversation with a demon is the core of the episode, and they sell it well. Dean and Casey seem believably open to what the other one has to say. As the saying goes, politics makes strange bedfellows (so does misery and war).

There's more plot; turns out the priest is a demon too, and Casey's lover. When the priest tries to strangle Dean, Casey begs him not to. Only Sam arriving with the Colt and shooting the priest saves Dean's life. Dean tries to warn Sam not to shoot Casey, but Sam isn't listening. Dean wanting to spare this demon's life, and Sam's ruthlessness, is a sign of how these characters have evolved. The episode also highlights Jared Padalecki's range; earlier there's a hilarious sequence when Sam gets caught breaking into an office and is both competent and fumbling. Here, he's terrifying.

In prior seasons, it's been Supernatural's usual M.O. to end episodes on Sam and Dean. "Sin City" ends with Dean confessing his fears about Sam's nature to Bobby, and Ruby further entangling Sam in her plans. Sam and Dean seemed easier with each other this week, but the rift is (alas) still there.

This episode seemed cluttered at times, but it was genuinely thought-provoking and memorable, and once again left wondering why more people aren't watching this show.

Episode 3x04, "Sin City"

Writer: Robert Singer and Jeremy Carver

Director: Charles Beeson

Guest stars: Robert Curtis Brown, Sasha Barrese