I’d become wrapped up in the first chapter of Twenty One, an "online virtual horror experience" from the creators of the "extreme" haunted house, Blackout. An ongoing series that first premiered at the end of last year, Twenty One is essentially designed to induce a state of paranoid terror in the player. Cryptic texts, interactive requests, and profoundly disturbing calls and videos manipulate you over several days into feeling like you’re being watched and are in danger at literally every moment. (How effective is it? I bought a baseball bat on my second day "just to be safe." How addictive is it for horror fans? I’m now in the middle of chapter three.)

"That is our version of an alternate augmented reality [game]," Blackout co-creator Kristjan Thor tells me over the phone. "There’s a lot of people doing extreme haunts. Now we’re saying: with all this technology, how can you re-think it in a way that anybody can [experience] it with their own phone and text messages and things like that?"

"Within two weeks, there was a line around the block for it."

It sounds like a simple enough proposition, until you dive into how visceral and physical a real-life Blackout show actually is. When the first production debuted in 2009 as A Midsummer Nightmare Haunted House, the scene was filled with jump-scare fests that simply lined audiences up and ran them through as quickly as possible. Whether a home-grown local haunt or a theme park riff like Universal’s Halloween Horror Nights, they were largely passive, with participants able to keep the scares comfortably at arm’s length. But Thor and co-creator Josh Randall, who’d previously worked together creating immersive theater productions of Shakespeare and musicals, wanted to elicit a different set of emotional responses. "Blackout was really our first time very specifically specifying that we were trying to do something fear-based," Randall says. "Within two weeks, there was a line around the block for it."

In Blackout shows, audience members must sign a waiver absolving the production of any responsibility, are given a safe word, and then sent through the production totally alone. There they can be subjected to scenes of extreme horror and violence, can be touched and shoved around by actors, and in some cases have even been waterboarded — an experience that director Rich Fox captured in his unnerving Sundance documentary The Blackout Experiments. It’s about crossing a line and getting into somebody’s head on a psychological level, and despite — or perhaps because — of its nefarious reputation, the show has become a name brand in the community, with Blackout spreading to Los Angeles and San Francisco. (There was even an invite-only event at this year’s San Diego Comic-Con.)

The popularity of Blackout has led other attractions to pick up the gauntlet of the "extreme haunted house," to the point where shows that test one’s sanity and endurance have become a subgenre in their own right. There are plenty of examples to pick from across the US, peaking with the infamous McKamey Manor in San Diego — an 8-hour endurance test with no safe word that has been accused of intentionally putting people’s safety at risk.

"What’s the next thing that nobody’s doing now with immersive horror?"

But while that may be the cottage industry that Blackout helped build, it’s clear that neither Randall nor Thor are particularly enamored of the brute force tactics those kind of shows employ — and Blackout productions have evolved appropriately. "We’ve been pushing into a little bit more of a psychological experience," Randall says, "and potentially trying to move away from the reputation we have as more of a torture porn environment." This October, the duo are actually building upon some of the more game-oriented elements in their shows for a Blackout escape room experience taking place at San Francisco landmark — and Kink.com headquarters — The Armory.

"It was fun when we started because we were doing something new," Thor says of the way the scene has evolved, but now that other productions have played catch-up their focus has turned toward expanding Blackout’s reach through new mediums. "It’s time for us to keep pushing, and think, ‘What’s the next thing that nobody’s doing now with immersive horror?’ This cross-platform methodology is our way into that."