“Everyone wants an alter ego who can do stuff they can’t.” So speaks Mark Hogancamp. He has a powerful incentive to focus on the contents of a parallel existence. Ten years before Jeff Malmberg’s cameras found him, he, aged 38, had every memory beaten out of his head after five men pounced on him outside a bar. He spent nine days in a coma, then forty in hospital relearning how to walk and talk from scratch. Of his life until that point, “only single frames” were left.

So far, so tragic but let’s return to that point about alter egos. When the Medicaid ran out, Mark, a talented artist before the attack, developed his own form of therapy. He built a miniature World War II-era Belgian town, which he christened by combining the first syllables of his name with the first syllables of two beloved female names (Mark + Wendy + Colleen = Marwencol). He used anything he could get his skilled hands on to furnish the town with all plausible conveniences, and a few implausible ones. A time machine is made from an eviscerated VCR player, its control panel is a Nokia phone cover and the seat a phone holder. The whole effect is a masterpiece of industry and attention-to-detail. Imagine a tiny Borrowers-style universe that doubles as a constant visual reminder of Mark’s need to hide in fantasy.

If the infrastructure of Marwencol is one source of awe then its inhabitants are another. The town is populated by dolls, each possessing a well-developed character and backstory. Some are fictionalised versions of the people he knows while others are fantastical creations. Storylines are devised and photographed and, once again, provide a mirror to his mood. Mark’s yearnings for female companionship materialise in weddings and love triangles while violent fights take place when Mark is angry about what happened to him.

Malmberg got ninety percent of his film’s quality by stumbling upon Mark Hogancamp. He adds the extra ten percent by whole-heartedly embracing the logic that governs Mark’s two-pronged reality. The narrative is broken into sub-titled chapters, each introduced by a doll propping up a cue card. Malmberg himself ends up with a doll incarnation running about in Marwencol. This is an honour reserved for those who have earned Mark’s trust.

Although mainly a showcase for Mark’s story, told through his robotic monotone and the scanned-in photo narratives that provide a timeline for Marwencol, Malmberg successfully provides the social context to Mark’s strange life through a cross-section of revealing interviews. Supportive friends and family talk of Marwencol almost as seriously as Mark does, while a doctor gives the blunt lowdown on the physical and mental damage he has suffered.

What is truly compulsive about this documentary is its timing. At ten years since the trauma and the consequent creation of Marwencol, Mark is ready to challenge the confines of his bubble universe. The film has progressed incrementally to this narrative pivot reflecting Mark’s slow return from the fringes of life. At the cusp of a big personal leap, he is self-aware and conflicted. “I don’t want to get hurt, mentally or emotionally or physically ever again”, he says. It’s a sentiment people frequently voice, but most have never had their worst fears come true in such violence.

Having started the film by detailing the attack in all its senseless brutality, Malmberg ensures that when opportunity comes knocking for Mark, you’ve never wanted anything to work out so badly. The temptation to print a T-shirt with his face and the words, “Go on, my son” written underneath is immense.

By leading the audience gently to this point and by clearly illustrating Marwencol as a work of creative genius and refuge from the storms and uncertainties of real people, Marwencol does an incredible thing. It shows mental illness as a logical response to terrible events. But more than that, it provides a rounded character study of an extraordinary man, it shows how kindness can mean colluding in someone’s fantasy world, and it shows how (although in one respect trauma never disappears) a traumatised person can develop around this bullet in their brain.

In an industry saturated by films that claim to be about issues they merely name-check, Marwencol is an unmissable work of documentary and humanity. I defy anyone to watch it and not come away feeling deepened, humbled and hopeful in a way too profound to fully describe.

Marwencol is now available on Netflix. Contributor Sophie Monks Kaufman can be followed on Twitter @sopharsogood.