On Halloween, Sam (Jared Padalecki) and Dean (Jensen Ackles) are on what looks like a standard job, investigating deaths in a small town. The episode starts unpromisingly, but then ratchets things up, proving again that Supernatural is one of the more intriguing genre TV series currently on the air.

As with last season's "A Very Supernatural Christmas," the familiar trappings of a holiday take on terrifying (and bloody) new associations. First up is the death by razor blades in candy, a take on a familiar urban legend, and then apple bobbing at a teenager's party goes horribly, horribly wrong. Sam and Dean, who often pose as something they're not even when it isn't Halloween, put on their FBI costumes and get to work on what looks like a witch hunt.

The first quarter of the episode drags, something no amount of intricate razor blade gore shots can disguise. The teenagers at the party use words like "rad" and "lame" and sound like caricatures, there's a cheap joke about Dean lusting after an underage cheerleader, and the staging of the apple-bobbing scene is awkward. But the real strain in credibility is that Sam Winchester doesn't know the proper pronunciation of "Samhain" and that Dean Winchester doesn't know who Samhain is. These are two guys who have spent their lives researching and hunting the supernatural, and the scene feels like a clumsy way to shoehorn in exposition.

Turns out the witch at work is hundreds of years old, and is working a spell to raise Samhain, a demon so scary he is, says Sam, "the reason Halloween was invented." When Samhain rises, he'll bring every spooky, scary thing with him. The episode starts to pick up fast from there. When Sam and Dean go to the high school to investigate Tracy, the suspected witch, there's a powerfully done moment when Dean has a very brief hell memory flashback, triggered by a piece of student artwork. Sam and Dean talk to the art teacher, Don, who confirms their suspicions of Tracy, who has been creating grisly artwork and acting out violently.

When the episode really gets started is when Sam and Dean get back to their motel to find Castiel (Misha Collins) and another angel named Uriel waiting for them. Sam's fumbling eagerness to meet Castiel is poignant – Sam believes in God and seems to crave Castiel's approval, while Castiel hesitates to shake Sam's hand at first. But then he gives Sam a double-handed clasp, saying he's glad Sam has stopped using his demonic powers. Uriel, impressively portrayed by Robert Wisdom ("The Wire"), is less friendly, standing with his back to the room as he makes terse, disdainful statements. Uriel, Castiel says, is "a specialist." In order to prevent Samhain from rising, the Uriel plans to destroy the entire town. The rising is one of the 66 seals that the demon Lilith is opening to bring about the return of Lucifer and Armageddon.

The interaction between Dean and Castiel here is terrific, as Castiel argues the bigger picture, twelve hundred lives lost in order to save billions, and Dean fights to save the twelve hundred lives. Dean says he and Sam will stop the witch, that there's no reason to destroy at entire town. The angels agree to give them a chance. There's another winner of a scene when Sam and Dean get back to the Impala and Sam expresses his disappointment in how the angels were. Sam is starting to doubt his faith -- "this is what I've been praying to?" Dean, who didn't think God or angels existed until he came face to face with Castiel, tries to encourage Sam not to give up his beliefs. "Babe Ruth was a dick, but baseball is still a beautiful game." This season has been working the shades of gray and ambiguous morality. Are the good guys all good? Can good be accomplished by using something evil?

The episode takes another twist when Sam and Dean discover that Don the art teacher is a warlock, and then things get even twistier. The boys go to rescue Tracy, who Don is about to sacrifice, and shoot the warlock. Tracy starts the episode as the cute cheerleader, becomes a suspected villain, then a potential victim; once she's saved, she turns out to be one of the villains after all, and a powerful one. Samhain possesses Don's body, and kills Tracy.

Meanwhile, Uriel and Castiel have a cryptic conversation about Dean's "potential" and their "true orders." The scene also reveals Uriel's disdain for the importance of human life and Castiel's disagreement with that viewpoint. Sam and Dean follow Samhain to the cemetery (with another one of those brother-to-brother talks in the Impala that the show always serves up so beautifully) where Samhain plans to open a portal to the underworld. While Dean fights the undead (because what is Halloween without Dean fighting the undead?), Sam faces off against Samhain. After telling Dean he was done using his demon powers, Sam uses them to exorcise the demon. The look that goes between the brothers as Dean sees Sam use his powers is an entire epic conversation without words. Sam has seemed remote this season, and it's great to have Sam and Dean working closely together and having honest conversations about faith, but the conflicts and difficulties are far from over.

There are two end caps for the episode, a conversation between Uriel and Sam and one between Dean and Castiel. The ep had a lot of Sam and Dean interaction, but the show is also playing on a broader canvas, and the two scenes separate the brothers, putting them each with their own angel, even while Sam strongly expresses that he's in Dean's camp. Uriel reprimands Sam for using his powers, and Sam angrily points out that he saved people by doing it. "My brother was right about you. You are dicks," Sam says, and Uriel threatens him, saying that the only reason he doesn't smite Sam on the spot is that he's useful. The scene echoes Dean and Castiel at the end of the second episode of the season, "Are You There God, It's Me Dean Winchester," where Dean insults Castiel and Castiel reminds Dean that he took Dean out of hell and he can send him back.

Whether either angel can, or would, make good on those threats, we don't know. Uriel also tells Sam that Dean should "climb off that high horse of his. Ask Dean what he remembers from hell." This furthers the hints of a dark secret about Dean, first raised in the murky exposition for why Dean got the ghost sickness in last week's "Yellow Fever." Does it connect with why Dean's eyes bled in season one's "Bloody Mary"? Is it because Dean "uses fear as a weapon"? Or did he do something nasty in hell?

The other cap is a quiet scene as Dean and Castiel sit on park benches, watching kids playing on a swing set. The scene further underscores the differences between Uriel and Castiel. Castiel expresses his doubts about what's right and what's wrong. He also reveals that the real purpose of the mission wasn't to annihilate the town – he and Uriel were supposed to follow whatever Dean told them to do, that it was a test for Dean. What role Dean is supposed to play, and what role Sam will play, we'll have to wait and see.

The episode brought some answers but also deepened the season's mysteries.

Episode 4x07, "It's the Great Pumpkin, Sam Winchester"
Writer: Julie Siege
Director: Charles Beeson
Guest stars: Misha Collins, Robert Wisdom, Don McManus, Ashley Benson