One of the biggest issues when people talked about the third season of “The Flash” was the shift in tone. The first two seasons saw Barry Allen (Grant Gustin) excited by the thought of protecting the city and curious about his powers – a stark contrast to the show’s sister series, “Arrow.” But then the third season got progressively darker – necessitated by Team Flash’s frantic search to save Iris (Candice Patton) from a future death by Savitar and ending with Barry sacrificing himself to the Speed Force to protect Central City from being destroyed.

“In the midseason finale – where we saw the future, and Iris dying – it was a great midseason finale but the problem it made for us was that we started to realize that to keep up that tension it sort of had to get darker and darker. I don’t think it was anybody’s intention to take it as dark as it got,” series executive producer Todd Helbing tells Variety.

Helbing and the team at “The Flash” know that a lot of what set the show apart as something special in its origins was that it was lighter fare. So they are taking great lengths to get back to those essential basics of the show.

“When conversations started about Season 4, everyone had a desire to get back to the fun – and have Barry be fun,” Helbing says. “Barry going into the Speed Force, it was a heroic sacrifice, but it also allowed us a way to bring him out of it and have an experience that will make him more light going forward.”

Here, Helbing talks with Variety about the new season 4 Barry,

Barry certainly looks like he has seen some s–t while in the Speed Force. What’s his mindset like when he gets out?

When he gets out he’s not exactly the same. What he experienced has a long-lasting effect on him and changes who he is. It lets him finally move past all the baggage he was carrying. I would say tonally the Season 4 premiere feels more like the first three seasons, and it’s episode two where the fun quotient really kicks in.

Iris has taken on a leadership role in Team Flash. Is this her just helping to pick up the slack with Barry gone, or has she found her calling leading and coordinating the team?

I think both. On top of Barry being gone, Caitlin [Danielle Panabaker] is gone. With Kid Flash [Keiynan Lonsdale] and Vibe [Carlos Valdes] as the resident super heroes, they need someone back in the cortex, and it was the perfect opportunity for Iris to come in and become team leader and drive the ship. It also allowed her to sort of deal with Barry not being there.

How are Kid Flash and Cisco handling being the resident super heroes? 

Cisco was always sort of hesitant to go out in the field, but he doesn’t have much of choice. He’s been thrown into fire and he rises about it. He and Kid Flash are a great team, and to see them work in tandem is a lot of fun.

Last season we saw the rise of Killer Frost, and then she left at the end of the season. Is she still trying to find a permanent cure, or is she learning to deal with the Killer Frost side of herself?

Like Barry, Caitlin had to go figure out this new life that she had. In the six months she’s sort of figured out who she is. It’s a little bit different than Caitlin Snow. When we find her she’s working in a bar that’s not quite the most upstanding bar around, and it’s a nice hint at what’s happened to her and how she’s going to move forward.

There were multiple references last season from characters who traveled from the future that The Flash would face off against Clifford DeVoe aka The Thinker. Why was he the choice for the first non-speedster villain?

In the long list of metahumans that we can have, some feel like they work better in an episode, some feel like they have more of an episodic arc, but The Thinker has been a guy who’s been on the board since Season 1. When we knew we didn’t want to do a speedster, there was such a breadth of new challenges that somebody with super intelligence could pose to Barry and the team. His powers sort of allow us to not have Barry fight the same sort of villain. He presents a completely new set of obstacles, and tonally that was exactly what we were looking to do.

“The Flash’s” fourth season debuts on the CW Oct. 10 at 8 p.m.