The Flash: Tom Cavanagh Talks Delivering on Showrunner Eric Wallace's "Visceral Horror" Tease

Season 8 of The Flash has seen the popular The CW series take on something of a horror vibe. Perhaps most obvious with the arrival of Deathstorm earlier this season, Central City's heroes have been dealing with darker challenges and foes, all influenced by different kinds of horror. Series showrunner Eric Wallace even previously promised that, before the season ended fans would get a taste of "visceral horror" and that tease paid off in tonight's penultimate episode of the season, "Negative, Part One". Now, series star Tom Cavanagh is opening up about delivering on that tease and how it just worked.

Warning: spoilers for this week's episode of The Flash, "Negative, Part One", beyond this point.

This week's episode saw a bit of emotional whiplash when it came to the story of Eobard Thawne/Reverse Flash (played, in different versions by both Cavanagh and Matt Letscher). While Letscher's Eobard had more or less redeemed himself and started on the path of being a good guy, in his prison cell on Lian Yu, Thawne (Cavanagh) was approached by Deon/Still Force (Christian Magby) — and very early on in the episode is killed, aged centuries in an instant. But that stunning moment ended up not being the end of Thawne. It turns out that when Barry took Thawne's speed, it erased the Negative Speed Force, destabilized the other Negative Forces, and sent them on a mission to get revenge on Barry (Grant Gustin). The Deon we've been seeing this season is actually Negative Deon and he's responsible for making Iris sick so that it would, in turn, weaken the rest of the forces. While that's an extremely villain thing to do, it still gets worse. After Eobard (Letscher) gets speed powers — thanks to a power share from Meena (Kausar Mohammed), Deon uses that, by way of sacrificing Iris, to resurrect the Thawne fans are most familiar with. Cavanagh's Thawne literally emerges from Eobard, back and more powerful than ever.

Yes, you read that right, but it's far more striking than simply "emerging" from Eobard. Eobard screams in pain as Thawne tears his face off to emerge from inside of him and lo, the moment of visceral horror promised by Wallace arrives. For longtime fans of the series, it will remind them of that comment Thawne made seasons ago, that one would never know what face Thawne might be wearing when he comes back but this ended up literal — and Cavanagh told us that while the plan came from the writers, it's not something he took lightly.

"I mean, you'd have to talk to Eric in the writer's room to see if they tracked that far back, and I'm going to say, I'm sure they did because of the preparation and the dedication they have to these storylines. But, in my head, it was like, 'Yeah, I'm not saying that lightly, It's not a throwaway,' and it feels like you always have to be careful, that you're like, 'Oh my God, what season are we on?'" Cavanagh said.

Cavanagh went on to explain about the importance of having a plan, something that he says The Flash can always give itself credit for, but he also says that, in some ways, this horrifying turn of events in "Negative, Part One", takes things back to a similar horror from Season 1 of the series in that you can't trust what you think you can.

"When you come down to it, it's season one again, in many ways," Cavanagh said. "It's the mystery and the horror of finding out that the thing that you thought you trusted, you can't trust because evil lurks there. It's the same thing. We're [eight seasons along] but ultimately that very moment you're talking about is reminiscent of when I put my hand through Cisco Ramon's chest, and it's scary, and horrifying, and visceral, shocking, and I don't use visceral as a pun there."

He continued, "But those are the moments that you want to tell, but they work the best when you're not doing them to show them up, and when they're supported by story, and I feel like in season one, that was definitely completely supported by story, and I feel it's the same the same thing with those moments that you're talking about here. Those moments work best when they're supported by story and the writers' room was prepared with the story and so I think it worked."

The Flash airs Wednesdays at 8/7c on The CW.