Robert Aguirre-Sacasa talks with THR about the evolution of The CW's breakout hit and what's next following the sophomore season finale.

Riverdale, 2017's surprise CW sensation, returned last fall for a second season with a new genre and nearly twice the number of episodes. Gone was the murder-mystery format that had Archie, Betty, Veronica and Jughead hunting Jason Blossom's killer. In its place was a Zodiac-inspired serial killer yarn wrapped around a mafia movie.

The genre-bending action of season two came to a conclusion Wednesday with Betty's (Lili Reinhart) dad (Lochlyn Munro) locked up behind a pane of glass — Hannibal Lecter-style — and Archie (K.J. Apa) in handcuffs and arrested for murder, seemingly at the behest of Veronica's (Camila Mendes) father, Hiram Lodge (Mark Consuelos).

Showrunner and series creator Robert Aguirre-Sacasa spoke with The Hollywood Reporter about shifting from 13 episodes to 22, reinventing the show every year and where viewers might want to look for clues about season three.

One of the biggest differences between seasons one and two was the episode count. This year, Riverdale ran 22 episodes, nine more than last season. What were the challenges that came with the expanded order?

Even more than the increase in volume, we sort of shifted genres. We went from a murder mystery — who killed Jason Blossom? — which was investigating something that had already happened, to the Black Hood story, which was a serial killer story with a present-day threat to the kids and the town. That's a little bit more ambitious, and the genre shifts from a murder mystery that is investigating something in the past versus capturing a killer that's actively shooting your classmates.

Halfway through the season, we hit pause on that story and shifted to Chic (Hart Denton), which was a more domestic suspense story for the Coopers. Then we brought Hiram to the forefront, exploring the mafia crime, before returning to the Black Hood. We put the challenge to ourselves of exploring different genres, to not be telling the same story again or — God forbid — a lesser version of the Jason Blossom story, which I thought was a great whodunnit. It's hard to do that twice and have the same resonance.

So, the difference in the writers room was more about the genre than the episode count?

Without question, it's harder to fill 22 hours of television versus 13 hours of television. That's just harder to do, but we almost change genre week to week. "This week, it's a musical. This week, it's a horror movie. This week, it's The Godfather. This week, it's a kidnapping thriller. This week, it's the Blossom gothicness." The idea is keeping it fresh and telling a story for a big cast of characters.

With the finale, there does seem to be at least some resolution with the Black Hood and with Betty swearing off darkness. Is this the end of her infamous black wig?

For two seasons, we've been exploring Betty's darkness, and I think that will always be a part of her character. It felt like the black wig did take on a life of its own. With the darkness, either Betty was denying it or it was controlling her. There was a struggle to understand it. I think that will continue. Again, rather than do another season of Betty struggling with her darkness, she's dealing with it another way or turning away from it or controlling it. Lili is such a wonderful actress that you, of course, want to give dark, dramatic material to. But I was so happy to see her in the finale smiling in the hotel room and walk away from the darkness that I don't want to deny that part of her as well.

There's an explicit homage to The Silence of the Lambs in the finale with Betty and her father. Hal Cooper takes on the Hannibal Lecter role in the scene. Might there be more to that in terms of his relationship with Betty going forward?

I can completely see a universe where Betty is visiting Hal in jail but as much for emotional reasons as investigative, Silence-of-the-Lambs reasons.

The big cliffhanger with Archie's arrest seems to hint at a direct conflict between him and Hiram next season. Is that the next major conflict for the show?

Yes. This season, Archie was sort of intoxicated by Hiram — his power and the way he moves through the world and his ruthless ideals. Archie kind of came back to the good guys' side by the end of the season, but there are consequences for what he's done this season. He and Hiram are squaring off, so I think that will be one of the main conflicts of season three, for sure.

We also saw some big changes with the Serpents, with Cheryl (Madelaine Petsch) joining and Jughead (Cole Sprouse) taking over. Is this a new gang now, or have only some of the features changed?

I think that's a question we're going to have to address head-on very quickly. Is it the same Serpents, or have they changed? How many are there? What are they doing now? I think these are core questions that the show will address head-on.

You mentioned how season one took on the shape of a murder mystery and season two was more a serial killer story. Is that genre template idea baked into the DNA of Riverdale, and can viewers expect a new genre come season three?

Absolutely. I think what started in my mind as a traditional coming-of-age show quickly morphed into something that was a little pulpier, something that was more noir, something that had a suspense or crime element. Yes, in season one, we did a murder mystery, and in season two, we did a serial killer in a small town and The Godfather in a small town. Season three will have a high genre element like that. That's what the show is. It's not just about the Archie characters. It's the Archie characters put into a specific genre, and we see how they relate and survive and adapt.

If fans were searching season two for hints of what's to come in season three, in which episode would you suggest looking?

That's a really good question. I would look back at episode seven of this season.

Riverdale returns next season on The CW. What did you think of the finale? Sound off in the comments section, below.