Showrunner Erica Messer says Criminal Minds: Evolution serial killer Elias Voit was initially expected to be the villain of only Season 1.

"By the time we got to the end of Season 1, it just felt like there was more story to tell with him," Messer told UPI about Voit in a recent Zoom interview.

"He brought this energy to our team that was new. He really brought conflict and I know we have that every week with bad guys, but I thought this was something different," Messer said.

"The minute we had him say 'Gold Star' to Bailey (Matthew Glave) -- then he killed Bailey -- we knew we were going to fight to get him back for the second season and continue that story. [Gilford] keeps winning us over."

In Season 2 of Evolution, wrapping Thursday on Paramount+, the investigators are shocked to learn Voit had organized his deadly Gold Star network of murderers using a hypothetical psychological theory Agent David Rossi (Joe Mantegna) and Dr. Jill Gideon (Felicity Huffman) explored in a long-buried paper they deemed too dangerous to publish decades earlier.

While the latest episodes find Rossi overwhelmed with guilt that his theory has led to so much tragedy, he also is furious that he has to consult with the now imprisoned Voit to prevent further killings.

"It's so rare that we put our heroes in the danger that Joe was in at the end of last season," Messer said.

"Of course, he's having post-traumatic stress and not wanting to talk to anybody about it, trying to do it on his own, handle it on his own," she added. "He did a similar thing his whole life, basically, in terms of any time he has trouble, he doesn't want to be the squeaky wheel."

Season 1 of the show tapped into anxiety related to the real-life COVID-19 pandemic, depicting what Voit and other serial killers might have been up to during lockdowns.

Season 2 looks more at how unstable, violent and conspiracy-minded people find each other in the darkest corners of the Internet.

"We felt like it was an important journey to go on this year," Messer said.

She added it was essential for members of the Behavioral Analysis Unit to understand that, despite their best intentions, they were partly responsible for creating a new generation of killers.

"If the team was just blind and thought: 'Well, we've done nothing wrong. We're the heroes trying to stop this kind of behavior,'" then they wouldn't be able to fix the problem," Messer said.

Streaming service Paramount+ has turned out to be a more appropriate home than CBS for the darker, more complicated stories Messer and her writers wanted to tell.

"Rossi's nightmares, him having panic attacks and seeing Voit everywhere, I don't know if all of that would have lived on the CBS version," Messer said.

There also might not have been the time and patience for quiet moments with characters in therapy sessions, mourning losses or discussing their careers.

"I just feel like our pattern of cutting used to be different, and now we get to have an entire episode where J.J. (AJ Cook) and Prentiss (Paget Brewster) are in Garcia's apartment, contemplating whether Prentiss is going to quit or not, while [they're] high," Messer said.

"From the cases being connected to the characters' emotional journeys, I just think we get to dive in a little deeper in this version."

The Season 2 finale sets up the third season nicely, and most of the cast will be back, Messer added.

"We end the season with Rossi closing the door on Voit as he's ready to shift into a healthier mindset," she said.

"We end this year on Elias Voit in danger while he's locked up, and that tumbles us into the next season, which will pick up about six months later and a lot of things have happened and a lot have stayed the same."