It: Welcome to Derry showrunner breaks down the Stephen King spin-off's scariest episode yet: "This is the beginning of a descent into the depths of darkness, terror, and madness"

It: Welcome to Derry co-showrunner Jason Fuchs says the season's most anticipated episode is just the beginning of a much darker and more devastating turn for the hit series.

Warning: Massive spoilers for It: Welcome to Derry episode 5 below!

"It felt like...the audience has waited half the season. They've gone halfway through the journey with us," Fuchs tells GamesRadar+. "It felt like the right time to reward people with the character they've been waiting to see from the beginning, the guy who's on the poster. But it also felt from a storytelling perspective, like what was much more paramount at this moment in the story was that we've been going on this journey in fairly separate lanes with the kids and the grownups. And it felt like this was a moment where we're halfway through the season, more than halfway by the time we get to the end of this episode."

To a casual viewer, it might seem like the show has taken far too long to show Bill Skarsgard's Pennywise in all his creepy, clowny glory. But the true Stephen King obsessives know that Pennywise has been in the show since episode 1, and that we've seen him over and over again... just in different forms. In episode 3, It finally manifests as Pennywise, and we see the dancing clown for just a brief second before it tries to get Dick Hallorann to throw himself out of the back of a moving airplane.

By the time we get to episode 5, the kids of Derry are desperate to get rid of Pennywise, and so is the United States Air Force. It only makes sense for It to lure both groups into the sewer tunnels under Derry, and for both major plotlines to finally mesh. It's impossibly satisfying, and something we don't see too often in a Stephen King story: the adults know what's going on, and they believe in it just as hard, if not harder than the kids.

"It felt like, these plot lines have to start to converge," Fuchs explains. "They don't need to resolve. We don't need to answer every question that as an audience we might have, but we do need to start to see these paths intersect and understand how the stories relate and bounce off each other. And so that was really the starting point. It was not necessarily us saying, 'Okay, this is the episode where we're going to see Pennywise. How do we make that happen?'"

Oh, but we do. After using Dick Hallorann's Shining ability to get the location of Pennywise's hiding place from Taniel, the US Air Force set out for 29 Neibolt St (yes, that 29 Neibolt St) with the intention to reduce It's cage and contain It. We, the viewer, know that this isn't going to work, but it's just a relief to know that someone in power is not only aware of Pennywise, but is trying to put an end to his reign of terror.

On the other side of town, Lily, Will, Marge, Ronnie, and Rich are visited by a ghoulishly pale Matty Clements – who is somehow alive despite being killed by Pennywise in the first 10 minutes of episode 1. Matty tells his friends that he's been living in the sewers, where It likes to hide, and that Phil, who is killed in the theater at the end of episode 1, is still alive down there somehow. The kids set out for the tunnels, following their friend Matty... whose corpse is actually floating in the tunnels under Derry. In a terrifying turn of events (and maybe the coolest thing we've seen in the Muschietti It universe thus far), 'Matty' morphs into Pennywise right before their very eyes.

"This is the episode where it feels like It has to ratchet up the sense of threat," Fuchs continues, specifically pointing to the scene at the very end of the episode, where It succeeds in getting Leroy Hanlon to point a gun right at the head of his own son. "It has to use Will against his dad as a weapon in some way. Because Leroy is, as we know, the man without fear. He is, in fact, the perfect person to put in tandem with Dick up against It. That is a pretty potent combo. A guy who doesn't experience fear the way normal humans do, and a special [guy], like Dick Hallorann, who can, as we've seen in episode three, get inside the mind of the entity."

"It is sort of forced to change its plan a little bit here. It is forced to sort of find a way to answer that threat, and the way he does it is by throwing our kids, and specifically Will, into Leroy's mission into that path. That's sort of where the decision to introduce Pennywise in this episode came from, because it felt like It is starting to up the stakes, up the ante in terms of what It's throwing at our characters, it felt like that's a moment where It is going to revert to one of Its favorite forms, one of Its favorite manifestations, which is Pennywise."

Though General Shaw still refuses to explain exactly what his plans are, Leroy, a Major, and his buddy Paulie, a Captain, follow their orders and head into the tunnels. Dick follows suit, protected by his Shining ability (though not for long). There, It takes on a few forms: a zombified version of Uncle Sam, and even Leroy's wife Charlotte (who Paulie can't see). Leroy tells Paulie to shoot at anything that isn't supposed to be down there, which results in Leroy raising his gun at Will, who appears with the rest of the kids. Convinced that this is just a manifestation, Leroy pulls the trigger, but Paulie, unable to convince Leroy that he can see the kids, steps in front of the gun.

"And so that really was the thinking [for episode 5]. If It is gonna go there in terms of doing something as cruel as putting Leroy's own son in front of him," Fuchs says. "And really, what almost happens, there's still a tragic ending, but what almost happens, and what I think in some ways It wanted to have happen, was to see Leroy kill his own son. And what other guise would it choose for this kind of a mission than Pennywise?"

Just before Leroy fatally shoots Paulie, Dick encounters a manifestation of his grandmother and abusive grandfather in the bathroom of his childhood home. His grandfather is holding a black lockbox, something that Doctor Sleep fans know is the only thing that is able to keep Dick's sanity in check, and his Shining ability from taking over. Pennywise, however, through the guise of Dick's grandfather, opens the box. Dick manages to make it out of the tunnels, but he's no longer the same man he was before he went in.

"This is the beginning of a descent into the depths of darkness, terror, and madness that I don't think we've yet seen, certainly in the series, but even in the It films," Fuchs explains. "We are going to take some really big, dark swings, and the cast of characters are going to be put through the ringer. You think about where we leave them at the end of this episode – Leroy might not be able to feel fear, but he can certainly feel regret and tragedy. Things are not gonna get better. Things are gonna get darker before they maybe get better."

It: Welcome to Derry is airing now on HBO Max. For more, check out our It: Welcome to Derry release schedule, or, check out our guide to all of the upcoming Stephen King movies and shows you need to know about.