Riverdale made its first arrest in the murder of Jason Blossom, and yes, the suspect is the person nearly everyone has been suspicious of from the beginning.

Cheryl Blossom (Madelaine Petsch) was taken into custody by the Riverdale police at the end of the episode and admitted she was guilty — but likely not of killing Jason. First of all, it's only episode 2 and secondly, Cheryl is the closest person to the crime which automatically makes her too obvious of a suspect to be the actual murder. You all know how this works.

However, Cheryl may actually be guilty of having more than sisterly feelings for her dearly departed brother. The second episode of the CW drama gave a little more insight into the Blossom twins' relationship and it seems that the two may have crossed the line into romantic relations. Petsch confirms that feelings of incest aren't completely unfounded between the siblings.

Madelaine Petsch, <em>Riverdale</em>Madelaine Petsch, Riverdale

"On the set, we call it twincest," Petsch tells TVGuide.com "We do play on that just a hair. I've made it more so that he's the only person who has ever understood her and loved her unconditionally. She's never had that love before so she doesn't know how to feel about it."

The loss of such an important person in Cheryl's life will have a profound effect on the character as the series continues. For Petsch, it's easier for her not to attach labels to Jason to understand how Cheryl is grieving.

"She's never had a boyfriend before so this is just like, her person. He wasn't like her boyfriend or her brother, he was just her person," the actress explains. "She doesn't really have good parents. That's more where I go with it."

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While Petsch may not want to define it, the siblings' displays of affection in flashbacks will confirm to the viewers at home that they aren't your normal brother and sister. We've already seen them holding hands and sharing a milkshake, and it's supposed to be as creepy as it looks.

"We do some strange things so people can take from it what they like, but it's open to your own interpretation," Petsch says. "We [hold hands] in a more romantic setting. It's cute when you're like brother-sister! But we do it more like lovers would."

The Blossom twin twist is just another example of how Riverdale is pushing the boundaries of a typical teen drama. This isn't a show simply about teenage characters discovering who they are and who they want to be — there are dark secrets lingering beneath the surface of every character that will shape how the show develops. The Blossom development ups the ante from Archie's (KJ Apa) affair with his teacher and probes even further into the seedy world of this small town. Incest is definitely a more ominous theme than CW high school dramas have tackled before, but it goes a long way in showing that Riverdale is never quite what it seems.

What do you think of the twist?

Riverdale continues Thursdays at 9/8c on the CW.

(Full disclosure: TVGuide.com is owned by CBS, one of the CW's parent companies)