As a movie, Iron Lung is occasionally thrilling but mostly forgettable. It’s a small-budget horror flick that has some cool ideas and pulls them off in an extremely efficient way, creating a sense of tension that unfortunately never turns into outright scares. But the most important thing about it is what it represents. At a time when movie theaters are dominated by only the biggest blockbusters and smaller films are trying to forge their own paths, Iron Lung managed to make more than $20 million at the box office without the backing of a major studio. All it took was a lot of help from YouTube.

The circumstances around Iron Lung aren’t exactly easy to replicate. It’s an adaptation of an 2022 indie horror game developed by solo creator David Szymanski, and it’s written, directed, and executive produced by Mark Fischbach, better known as the YouTube star Markiplier. Markiplier is best known for his let’s play videos of indie horror games in particular, and he’s built up a surprisingly huge audience through that, with close to 40 million subscribers on YouTube. Three years ago, Markiplier posted a playthrough of the game that was viewed more than 14 million times. In 2022 Szymanski joked about Markiplier starring in an Iron Lung movie, a trailer dropped a year later, and now the final product is in theaters as Markiplier’s first feature film. In addition to being the creative lead behind the movie, Markiplier is also the star, which is a notable feat for a movie that mostly features one single person on camera.

The film’s premise is pretty out there: In a bleak future, a convict (Markiplier) is welded inside of an experimental submarine as punishment for his crimes. He’s tasked with exploring a moon’s ocean in search of… something. Oh, and that ocean also consists entirely of blood. Survive and he gets his freedom. The convict can’t see outside of the sub except by using an underwater camera that takes low-res images of the deep (blood) sea. So the experience of watching Iron Lung is mostly watching Markiplier swear, mumble, and hit switches, while steadily going insane from being trapped in such a hellscape. The movie manages to wring a surprising amount of tension from that format early on, but it really starts to drag and feel repetitive as the story progresses. One of the most pivotal moments is a drawn-out sequence of him drawing a map.

Iron Lung is very clearly based on a video game. It uses so many of the same conceits: a guide character who is mostly just a voice over a speaker; diegetic storytelling elements like instruction manuals and big displays that reveal how deep the sub is and how much oxygen is left; audio logs that reveal important plot details; and a gear upgrade midway through. Its cast even includes Troy Baker, the voice actor behind seemingly every video game of the last decade. All of these elements can work really great in the context of an interactive video game, but they feel much more clunky in a live-action film. That said, as a first feature film effort, Iron Lung shows a lot of promise, even if it never fully comes together in the end.

Despite this, Iron Lung is an unqualified success. It reportedly had a budget of just $3 million, and according to Deadline it finished second in the US box office over the weekend, raking in north of $18 million, a number that has since surpassed $20 million worldwide. That put it just behind Sam Raimi’s Send Help, a 20th Century Studios production, and well ahead of Amazon’s very expensive documentary about Melania Trump.

YouTubers successfully transitioning into other creative realms isn’t a new phenomenon, not even in Hollywood. Brothers Danny and Michael Philippou made the jump from YouTube to release two excellent horror movies in Talk to Me and Bring Her Back, both of which raked in tens of millions. But those movies also had the studio might (and money) of the A24 name behind them, whereas Iron Lung is a much more grassroots affair. Markiplier utilized his fervent fan base to reach out to theaters directly, ultimately leading to the film being featured on more than 3,000 screens, despite not having a distributor. He was able to turn one kind of popularity into a breakout hit in a completely different medium.

“There were just so many people that asked [the theater chains to screen it],” he told The Hollywood Reporter. “There were enough people that asked that people thought it was bots. At that scale, it’s hard for other people to imagine that so many people are asking.” In that same interview, he said that there’s a “still is a stigma against YouTube,” and he wanted Iron Lung to be successful in part to help break that barrier.

While that might help other big-name creators who want to get into film, it’s not a formula that will be easy for either filmmakers or studios to replicate. Budding horror directors can’t just amass a YouTube audience of millions first as a way of helping their projects break through, and there is an enormous difference between running a channel and making a blockbuster.

But the Iron Lung story does show the power of having an existing audience, and how the scale of online success has now reached a point that it can disrupt even the most established institutions, like Hollywood, and directly compete with the likes of Disney and Amazon. And with more hits like Iron Lung, that stigma will only continue to fade — and theaters might not look the same.