There are few things more immediately relatable than stepping on a rusty nail.

The sudden stab of pain. The instinctive inspection of the offending piece of metal. The brief mental calculation of just how bad this might be.

Then there is Carroll.

When Oliver Bernsen’s Bagworm introduces its protagonist, he is already a man seemingly determined to make his own life as unpleasant as possible. A sexually frustrated hammer salesman, conspiracy-minded malcontent and habitual misanthrope, Carroll has developed an elaborate worldview in which the world is broken, society is collapsing and everyone else seems to be conspiring against him.

Then he steps on a rusty nail.

It is, perhaps, the least surprising turning point in cinema history.

What follows is a grimy, grotesque and frequently darkly funny descent into paranoia, physical deterioration and self-destruction. Carroll’s body begins to break down, but so too does his already precarious grip on reality. The question becomes increasingly difficult to answer: is the world genuinely falling apart around him, or is Carroll simply becoming incapable of seeing anything beyond his own increasingly distorted perspective?

Bagworm is at its most effective when it refuses to provide an easy answer.

There is certainly a straightforward body-horror film lurking underneath all the grime. The rusty nail becomes the gateway to an infection that gradually consumes Carroll, providing Bernsen with ample opportunities for increasingly revolting practical effects. His deteriorating body becomes a physical manifestation of the rot already present in his life.

But the film isn’t really interested in asking whether Carroll is sick.

He’s obviously sick.

The more interesting question is whether the infection is responsible for his behaviour or merely giving physical form to everything that was already there.

Carroll is not an easy protagonist to spend ninety-six minutes with. That seems entirely deliberate.

He is petty, suspicious, angry and convinced of his own righteousness. His relationships with women, friends and strangers become increasingly disastrous, yet he repeatedly interprets the resulting hostility as evidence that there is something wrong with everyone else.

It is a particularly contemporary form of horror.

The world hasn’t necessarily turned against Carroll.

Carroll has simply constructed a worldview in which it must have.

This is where Bagworm finds its sharpest satirical edge. Its protagonist’s paranoia and resentment place him within the orbit of the modern manosphere, where personal failure can be transformed into political grievance and loneliness becomes evidence of a conspiracy rather than an invitation to self-reflection. Critics have similarly read the film as an exploration of toxic masculinity, male isolation and the tendency to externalise personal misery.

Bernsen’s achievement is that he doesn’t make this entirely miserable to watch.

Bagworm is often very funny.

Not necessarily comfortable funny, and certainly not always “laugh with the character” funny. Much of the humour comes from watching Carroll’s increasingly bizarre attempts to navigate ordinary social situations while apparently possessing no ability to recognise how thoroughly he is sabotaging himself.

The comedy works because there is something painfully recognisable beneath the grotesquerie.

We’ve all encountered some version of Carroll.

Perhaps not quite this version.

Hopefully.

Peter Falls gives the film an important centre of gravity. Carroll is repellent without becoming entirely abstract. There are flashes of vulnerability beneath the hostility, moments where the character seems less like a cartoon of internet-age masculinity and more like a desperately unhappy man who has spent so long blaming everyone else that he no longer knows how to examine himself.

That distinction matters.

Because Bagworm isn’t particularly interested in redemption.

It isn’t a story about a troubled man discovering the error of his ways and becoming a better person. Instead, it watches him continue digging, apparently oblivious to the fact that he is holding the shovel.

And then it makes the shovel increasingly disgusting.

The physical deterioration is where Bernsen’s filmmaking becomes particularly effective. The film’s grubby aesthetic gives the horror a distinctly tactile quality, while Carroll’s deteriorating body increasingly resembles the physical embodiment of his internal state. The world around him feels just as diseased as he is.

His house is decaying.

His relationships are decaying.

His body is decaying.

And somehow Carroll remains convinced that the problem is everybody else.

That is the joke.

And the tragedy.

Bagworm isn’t always as controlled as its best moments suggest. Its deliberately abrasive tone can become exhausting, and its third act doesn’t quite sustain the same combination of psychological unease and dark comedy that makes the earlier sections so compelling. Even critics who responded strongly to the film have noted that its various stylistic and thematic ambitions don’t always land with equal force.

But there is something admirable about the sheer unpleasantness of it.

Bernsen isn’t attempting to make Carroll conventionally sympathetic. Instead, he asks us to look at a particularly ugly form of contemporary loneliness and watch what happens when isolation, resentment and paranoia are allowed to feed one another.

The result is body horror with a distinctly social infection.

The rusty nail gets into Carroll’s foot.

The paranoia gets into his head.

And before long, it becomes difficult to tell where the disease ends and the man begins.

That is what makes Bagworm considerably more than another gross-out horror film.

It is a portrait of a man rotting from the inside out — and a world that may not be quite as responsible for the smell as he thinks.

SUFF #20

Bagworm screens as part of Sydney Underground Film Festival #20, celebrating the festival’s 20th anniversary at Factory Theatre, Marrickville.

For the full program and ticket information, visit the Sydney Underground Film Festival.

• Saul Muerte