Iron Lung is a horror film based on the video game of the same name, written, directed, starring, and produced by YouTube celebrity Mark "Markiplier" Fischbach. It had a limited run in theaters on Jan 30th, 31st, and Feb 1st, across the U.S., Western/Central Europe, Canada, Australia, and New Zealand. It made $18 million in worldwide box office on a budget of approximately $3 million. It received a 50% critic score and 89% audience score on RottenTomatoes, and a 6.7/10 on IMDB, indicating a mixed critic reception and moderately positive audience reception. The film was originally set to run in 50 theaters within the U.S., but a coordinated push by Fischbach and his fans expanded it to 4,105 venues across the globe.
Who is Markiplier? What is Iron Lung?
Mark Edward Fischbach, better known by his online handle Markiplier, is an American YouTuber with 38 million subscribers. He started his channel in 2012, building his reputation by playing horror video games, and "broke out" in popularity with the release of the first installment of horror game Five Nights at Freddy's. He branched out into variety content, most notably narrative filmmaking, with the narrative "choose-your-own-adventure" YouTube series "-with Markiplier" (A Date, A Heist, In Space). He has also been producing the horror anthology "The Edge of Sleep," released on Tubi in May 2025. Iron Lung is his first feature film, which has been in production since 2023.
Iron Lung, the video game, is a short horror game released on March 9th, 2022. Set in a post-apocalyptic future where an event called "The Quiet Rapture" caused all known habitable stars and planets to disappear, a convict is sent to search an ocean of blood discovered on a desolate moon, using a small submarine nicknamed the "Iron Lung." Videos of its gameplay garnered tens of millions of views after the major gaming YouTubers played it. It was practically engineered to do well as a "Let's Play" game; the gameplay is very simple, its atmosphere is perfectly unsettling, and it's short enough to be played to completion in one 30-60 minute video.
Iron Lung's Production
The film's cast consists of four people: Fischbach himself, Sean "Jacksepticeye" McLoughlin, a friend and fellow YouTuber, Caroline Kaplan, a long-time film producer, and Elle LaMont. Fischbach, who has released several YouTube videos about the movie and its production process, stated in 2024, "This has been the longest run of pure work that I've ever done in my entire life...[It's] been the most arduous thing that I've ever taken on. It has required the most of my concentration for the longest period of time than anything I've ever done."
In a statement provided to Variety, Fischbach explained his drive and rationale behind creating the movie as a solo project. "They said it shouldn't be done. Not that it couldn't be done, people have made movies before, just that it would be 'woefully unwise' to tackle writing, directing, acting and editing a movie myself. Showed them." Additionally, in a YouTube livestream for previous YouTube project Unus Annus, he explained that he "wanted to build the infrastructure for other creators to do something like this ... because nothing like this has been done through the 'traditional' methods." The film is distributed by Fischbach in the U.S., and by several companies internationally.
Review
I should start this review by saying that I have been a fan of Markiplier since 2016, so in some sense I was seeing this movie out of "loyalty" to him, if you would call it that. And that history with him did create or exacerbate a weakness of the movie: the acting. It's not glaringly awful, and Mark does have legitimate talent, but it's not there, at least not yet. When I watch his performance, I'm not seeing The Convict, aka Simon, I'm seeing Markiplier, the man who makes me laugh by yelling at video games. The other actors, primarily Caroline Rose Kaplan as Ava, give solid performances, although it's up to you if their performances are helped or hampered by the fact that we only hear their voices, barring a five-minute conversation through a blood-stained porthole.
The plot, relatively light, serves the movie well. I will refrain from a recap here, as I would certainly double the length of this article with it, but spoilers still apply. It captures the atmosphere of the game perfectly; the ship practically alive: groaning, sparking, shuddering, and as it sustains damage, it begins to bleed. The pacing has been a notable issue among critics, but that's the whole point of the movie and the game. You're watching a man become deadened to the horrors around him as he repeats his cycle around the sub. Camera. Map. Reposition. Move. The religious/hallucinatory thread felt overplayed, and a bit self-important, which does put a damper on the movie's last twenty minutes. If you go into the movie looking for a complex or engaging script, you are in the wrong place, although I would not fault you for being disappointed. Instead, you watch it to experience the atmosphere: sticky, nasty, desperate.
Speaking of the atmosphere: if there's one thing that recommends Iron Lung, it's the technical details. The sub was built in one piece on a mechanical rig, which shifts and rotates and flings The Convict around. The blood, which Fischbach claims accounted for "the most fake blood ever used in a movie," is ever-present, corrupting the ship and The Convict himself (as well as Fischbach, when he was hospitalized after too much of it got into his eyes during filming). The cinematography is of special note, capturing every inch of the panic, grime, and, yes, blood that fills the ship, and it provides several clever shots and moments, especially with its movement. The editing, too, is on point, letting scenes breathe, and strangling them when appropriate, including a couple dare-I-say inspired match cuts and other little flourishes.
If I have any major complaint about the film, it would be the audio. The mix is fine, and the microphone quality was fine, as well, but I had a hard time understanding the characters. Granted, all voices but The Convict's are heard either through a radio box or are distorted by hallucination, but there were several times that The Convict clearly understood a message that I could not. If subtitles were available, I would take them in a heartbeat, because I spent way too much time being taken out of the film by thinking "Wait. What was that?"
The Verdict
Iron Lung is a good movie. Simple as that. I would argue it isn't really a horror movie, except for hemophobes, but more of a thriller. It's not for everyone, but then what is, so if/when it ever gets a home release, give it 30 minutes of your time to see if it could pull you in. It's a strong showing for Fischbach, if not as an actor, at least as a director and storyteller, and it's a positive voice in the chorus of indie directors trying to make a change in the otherwise stagnant industry. I don't think I'll be watching it again soon, but it was a good time, and it was fulfilling to watch someone as passionate and driven as Mark pull something like this off.