Why Pennywise’s Warm Glow Is the Scariest Part of Welcome to Derry

Pennywise, Bill Skarsgård, and the Return of IT in Welcome to Derry

When Bill Skarsgård first appeared as Pennywise, the world saw what director Andy Muschietti noticed early on: that unsettling smile, the slight lazy eye, the feeling that something about him understood how to play a character that can look inviting, but still feel wrong. IT: Chapter One and IT: Chapter Two went on to become massive hits, with the first becoming the highest-grossing horror film of all time. So it wasn’t much of a surprise when IT: Welcome to Derry debuted this year as one of HBO’s biggest original series launches.

But watching it, we found ourselves less focused on the scares, and much like his victims, something more inviting.

The light.

Pennywise’s glowing amber eyes.

The warm glow of the Deadlights.

It’s the same color as a table lamp in the corner of your living room or a fireplace. It’s the same warmth of the light you turn on when the house finally settles, and everyone ends up at the table a little longer than planned. It’s the same kind of light that usually means “you’re safe here.”

In Welcome to Derry and the recent IT films, there’s a pattern you start to notice. When Pennywise is near, the light becomes warm, unlike the cold institutional fluorescents that we see in schools and hospitals. And not the blue-white of modern LEDs. The lighting is warm, golden, even, and inviting. That’s what makes it unsettling. He’s using the kind of light our nervous system trusts most.

The Firefly Scene and the Psychology of Warm Light

There’s a moment in IT: Chapter Two where Pennywise appears under the bleachers to a young girl in the dark. She’s already afraid. Already alone. And to make himself visible, he doesn’t use a flashlight or a phone screen; he uses the glow of a single firefly.

It’s such a small choice, but it says everything.

Warm light at low levels mimics firelight, the kind humans have gathered around for hundreds of thousands of years. Fire meant warmth, food, and people close; danger was kept at a distance. Even now, your body still reacts to that kind of light before you have time to think about it.

Warm light, around 2700K–3000K, tells your brain you’re in a private space. The kind of space where you kick off your shoes, pour one more glass of wine, and realize it’s already later than you thought. It can lower cortisol and help you relax as it signals the end of the day. Warm light makes you feel like you can let your guard down.

Cool light, 4000K and up, does the opposite. It keeps you alert. Focused. Awake. That’s why it shows up in offices, hospitals, and classrooms. It’s not bad. It’s just not where you rest.

So when Pennywise uses a firefly, it’s not just about being seen. He needs the girl to lean in. To feel like this moment, strange as it is, might be safe. He needs the light to tell her that, so he can set the stage for her to fear; the light does half the work for him.

The Auditorium Scene and Pennywise's Horrorifying Performance

In the Welcome to Derry season finale, Pennywise takes over the high school auditorium. At first, everything is lit cold. A spotlight draws all the children’s attention to a dead teacher being used like a puppet while Pennywise hides behind the curtain.

Then he steps out, and the light shifts; it turns warm.

Pennywise sings.

Pennywise dances.

Pennywise decapitates the teacher.

And then he places the children in a trance with the glow of the Deadlights. Once again, it’s the warm, familiar, comfortable light that signals danger, a complete flip of what our nervous system expects. We see his “performance” with the kind of lighting used for a school play or a concert. The same feeling you get when house lights dim and warm stage lights rise, and suddenly a room full of strangers feels like a shared private moment.

Warm light has a way of doing that. It makes public spaces feel intimate. It’s why restaurants glow at night, why bars look better after sunset, why hotel lobbies layer lamps instead of blasting overheads. They’re all trying to say: stay a while, this is your place for the moment. Pennywise uses that same language.

He’s not just terrifying his victims.

He’s hosting them.

And it’s the warm light that makes you feel like you want to be part of it.

How Welcome to Derry Uses Light to Invert Safety and Fear

Throughout Welcome to Derry, nighttime exteriors and institutional spaces stay cold. Blues and greens. Streetlights and moonlight. The kind of light that keeps you alert, scanning your surroundings, aware of every shadow.

But when Pennywise is near, there’s almost always a touch of warmth introduced.

That inversion is what makes him dangerous, and what makes the franchise so effective. Most horror teaches you to fear the dark and trust the light. Pennywise teaches you that sometimes the light you trust most is the one that will betray you.

• There’s a reason nurseries use warm nightlights instead of cool white bulbs.
• There’s a reason candles still exist even though we have better light sources.
• There’s a reason you relax when someone turns off the overheads and switches on a lamp.

Warm light tells your body it can stop looking for what might be wrong and that this is a safe space. You’re allowed to settle in. And when that signal is a lie, when the warmth comes from something that wants to hurt you, your brain short-circuits. Because the light is saying one thing and everything else is saying another, and you’ve been trusting that light your whole life.

Bill’s House and the Basement: Lighting as Emotional Storytelling

In IT: Chapter One, Bill is in his bedroom, missing Georgie. The room is lit by a warm table lamp, the kind of light that makes a space feel like a refuge and places us, the audience, in a state of compassion for him.

Then a shadow moves across the door.

He leaves that warm pool of light and steps into the dark hallway. Down the stairs. Into the living room, which should feel safe, yet it’s lit by another warm table lamp. The same signal again, before anything visible happens, that Pennywise is near.

Georgie’s figure runs past and disappears into the basement.

Down there, the light changes. A single bare bulb overhead, deep shadows radiating outward, corners you can’t quite see into; the worst kind of lighting for feeling safe. A single source can’t cover a whole space. You get pools of visibility and pools of blindness, and your eyes can’t quite reconcile them.

There’s also warm light seeping in through the basement windows from the street outside. It should help and make things better, but it doesn’t. It only adds more contrast and gives you more for your brain to try to process.

In one sequence, you move through every emotional register that light can create. And once again, the warm light,  the light that should mean safety, is what signals the threat first.

Warm Light Is Power: The Real Horror Behind Pennywise

Pennywise glows warm because warm light is powerful, not in a loud way, but in a quiet, automatic one. It works on you before you think about it, before you process what you’re seeing, before you even decide whether to be afraid or on guard. We are psychologically primed to feel safe, secure, intimate, and at home in warm light. And our nervous system believes it, even when everything else is screaming danger.

The people who made the IT films and Welcome to Derry understand that lighting is never neutral. It’s always creating emotional context. It’s always signaling something about a space and your relationship to it.

• Warm light creates intimacy and trust.
• Cool light creates alertness and distance.
• Single sources create vulnerability.
• Layered sources create comfort.
• Shadows create dimension.
• Flatness creates unease.

These are things you know intuitively and that you gain more evidence of as you experience life. Pennywise just makes it obvious by using it against every one of his victims.

The principles are the same in your own home. If a room doesn’t feel right, check the color temperature. If a space makes you uneasy, look at whether it’s lit by a single source or layered with a few softer ones. If your house feels institutional instead of intimate, it might just be that you’re using cool light where warm would serve you better.

The light you choose is doing something, whether you're conscious of it or not.

Warm light creates trust. That’s its power. That’s why it works. That’s also why you should understand it and make use of it intentionally instead of letting someone, or something, use it against you.