Mark "Markiplier" Fischbach in Iron Lung (2026) — *Credit: Markiplier Studios*

Content warning: Please be aware that Iron Lung contains frequent use of flashing light that may affect those with photosensitive epilepsy.

Mark "Markiplier" Fischbach has been a staple of the YouTube horror gaming scene since his debut in 2012. Now he's traded his computer screen for the big screen with his adaptation of David Szymanski's 2022 indie game Iron Lung. The Youtuber’s directorial debut is an eerie and blood-soaked descent into the unknown.

In the distant future, humanity has suffered through “The Quiet Rapture” – a cosmic event that has caused most of the universe’s stars and planets to vanish. The last vestiges of human life search for something, anything, that could hold the key to saving them.

On a desolate moon with an ocean of blood, a convict (played by Fischbach) is given a chance at freedom if he completes an exploratory mission in an experimental submersible. With only the voices of two scientists monitoring him for company, he must photograph what he finds. But something quickly becomes clear: he isn't alone down there.

It’s hard not to see Iron Lung as a one man show. While Fischbach has acted before – including starring in the Amazon Prime Video thriller series The Edge of Sleep – here he is a world away from his online persona. His character is a man in a seemingly inescapable situation, despite the deal he’s made with the scientists for his freedom. He's physically alone in this confined space – while outside lurks a massive, unknown force that becomes more hostile throughout the film. The performance conveys a growing desperation that builds to the point of madness by the film’s apex – with those necessary dark secrets haunting him, of course – and Fischbach does a really good job with it.

That isn’t to scoff at the few others we get to see and hear from in the film – particularly Caroline Rose Kaplan and video game voice actor Troy Baker, who play the scientists directing our doomed deep diver on his mission. Everything about them screams shady and unreliable, but they’re also the ones that hold the key to the convict’s possible freedom. For them this is about answers – not that there are any easy ones to be found here.

The film’s lack of concrete solutions may frustrate some, but for me it puts you in a similar position to the characters – one of helplessness in the face of the unknown. It drives home not only how alone our protagonist is under this ocean but also in the universe – and that extends to humanity as a whole. An under the sea Event Horizon (1997) would be an accurate, if simplistic, idea of the flavour of cosmic horror going on here.

This sense of isolation and helplessness is backed up by some bold and horrifying imagery, all drenched in blood. And, speaking of blood, when the practical effects kick in they are exactly as visceral and gooey as you would hope. The film reportedly used 80,000 gallons of fake blood – a record-breaking amount that saw Fischbach briefly hospitalised when the stuff temporarily dyed his eyes red. There's bleeding for your art, but this was being bled on for your art.

The rest of the production is solid if a bit rough in places. Andrew Hulshult's score is good and suits the film, but there are moments where just the environmental sounds – the groaning of metal and the distant rumble of something unseen – would have been more effective.

The film’s biggest issue is the pacing and run time. Two hours is a lot for such a simple concept, and twenty minutes could have easily been lost without impacting the story. It’s an overindulgence, but one potentially born out of love for the source material. Iron Lung is a passion project in its purest sense, with Fischbach even turning down a cameo in the first Five Nights at Freddy's movie (he would have been the security guard killed by the animatronics at the beginning of the movie) because it clashed with Iron Lung's production schedule.

But it’s a choice that has paid off. For a YouTuber, even one with a significant amount of influence, to independently co-write, produce, star in, direct, edit, and distribute a film on a worldwide scale is impressive. To then also have that film hold its own in the US box office against a new film from Sam Raimi is an even greater achievement, however you slice it. This doesn't diminish the film's flaws by any means, but it certainly indicates that Fischbach has a lot of potential in the industry.

An atmospheric adaptation, what Iron Lung lacks in polish it more than makes up for in ambition, enthusiasm, and passion. Here’s hoping it’s the groundwork for more great things from Mark Fischbach as a creative force in the future.

Iron Lung has a limited run in cinemas and will be coming soon to digital download.