Conjoined twins are about as rare in movies as they are in real life, and when they do appear they're usually background characters in fairgrounds and played for comic effect. In Hitchcock's The Ring they each want to sit in opposite sides of the church at a wedding, and in Tod Browning's Freaks they cheerfully plan separate futures and encourage each other to come visit them once they are married. How many films can you think of in which conjoined twins are the central characters and their situation taken seriously? I can think of only one, and you're reading about it right now.

It can't have been an easy pitch, a low key character drama about conjoined twins and the friendship they develop with a young prostitute, written by two real-life twins who are also planning to play the dual lead roles and whose only previous movie credits were supporting parts in Hellraiser: Bloodline. Oh, and one of them wants to direct it, too. Despite the potential gimmick factor of a film made by, starring and about twin brothers, I would like to think those who were bold enough to invest the $500,000 it took to get it to the screen did so because they saw real potential in the material and had faith in the filmmakers. I'd also hope that, despite obvious fact that the film was never destined to be a big money spinner, they'd believe that the finished film justified their faith.

When I received the preview DVD it had been some time since I'd last seen the film, my first exposure to it being at a cinema screening I was involved in organising. Like many who came to the film then, I was drawn by the very thing that presumably kept the mainstream audience at a distance – the unusual nature of the subject matter and its reputation for being strangely compelling. A few years on I remember being utterly captivated by the film, but could not recall exactly what it was that made it so damned intriguing. Watching it again it took just a couple of minutes for total recall to kick in. There's no loud hook here, no Matrix-like bang to make sure even those with short attention spans stick with the film during the expositional sequences that follow. It's all little things, suggestive moments that have a semi-abstract quality the first time round but which actually make sense on a second viewing – the opening shot that shifts from negative to positive, the taxi driver with a hook for a hand, the glum-looking elevator man of 52 years standing who asks young call-girl Penny if she is here to see Jesus, and his suggestion that if the door she is standing in front of looks like all the others, then it's not the one she wants.

The hotel in which the elevator man works, at which Penny has just arrived, has an atmosphere of instant intrigue, a little dash of Lynch, a dab of Barton Fink, and music that, in the manner of Blade Runner's quieter moments, seems ooze quietly from the paintwork rather than underscore the action. Penny finds the right room and her allotted client, one Francis Falls, but when he emerges from the bathroom he is not one but two, Francis and Blake, joined mid body with three (and a half) legs between them and an arm apiece, well dressed, hesitant, gentle of voice and calm in expression. There is nothing sensational about their introduction or presentation, but Penny flees nonetheless. In the scenes that follow, it is suggested that there is far more to her present state of anguish than the shock of her first look at the Falls twins.

It's the following scene where the tone of the film is really set, and where you'll either go with the film or tune out. The twins seem largely unperturbed by Penny's departure, and settle down to quietly mark their birthday with a cake of different halves for differing tastes, despite a shared stomach. They are interrupted when Penny returns to the hotel room, not out of remorse for her actions, but because she forgot her purse. Her initial shock now overcome, she asks to borrow their phone, and while she makes her call the twins return their full attention to the cake, only occasionally looking up at her in uncannily perfect unison. Following the call she sits with her head in her hands, which the twins respond to by silently offering her a slice of birthday cake, which she gratefully accepts. As she sits and waits for the return call, the brothers drift off to sleep on the pushed-together single beds.

Nothing about the above may sound particularly exciting, but the way it plays on film is just... man, I'm still stuck for words to describe just why it feels so perfect. The brothers themselves are a major factor here, beautifully underplayed by Mark and Michael Polish, who are locked to each other by an invisible rig so effectively that it's hard to imagine where their hidden body parts are. Their soft-spoken, wide-eyed uncertainty, their secretive whispering to each other and their coordinated behaviour makes them instantly fascinating and sympathetic characters. In just this one scene we are able to see past their condition and connect with the people affected by it.

The friendship that develops between the Falls brothers and Penny is the core of the film. While we are to some extent in familiar territory – movie prostitutes always seem to have a heart of gold – the relationship is handled with such sensitivity and Michele Hicks is so assured as Penny that this never seems to matter. Slowly we learn a little about the twins, that have come to town find the mother who long ago abandoned them, that Francis is not as physically strong or healthy as Blake and relies heavily upon him, and that Blake loves his brother but still secretly longs for the freedom of separation, feelings that come to a head when he begins falling for Penny.

Penny's next encounter with them finds them at their most relaxed. It's Halloween, the one night of the year they are able to interact with so-called normal society without attracting undue attention, as they go trick-or-treating in the most convincing Siamese twin get-up Penny's waitress friend has ever seen. They even follow Penny to a party, where the film comes close to over-literalising their feelings as two guests in Siamese twin fancy dress untie their bonds and separate while the brothers mournfully watch on. Twice more the sublime subtlety exhibited elsewhere is allowed to slip, first in the shape of Penny's lawyer friend Jay (dubbed by the filmmakers "The Exploiter"), who excitedly suggests a whole slew of ways that the brothers can exploit their condition and in the process comes to (a little crudely) represent the media and society at large. This is brought home a short while later when the fleeing pair stop to catch breath in a park, are find themselves stared at and photographed through a fence like caged exhibits. But even these slips into overstatement are well handled and have later resonance – once again, a second viewing adds to their meaning and purpose.

For the most part suggestion is the order of the day. A duet in which the brothers jointly play a guitar and sing to Penny, for instance, at first seems like something they have learned to do to pass the time – only later, when the dots are connected to their past, is the significance of this moment fully appreciated. It's the small details that prove the most affecting and memorable, appropriate given that the two brothers communicate through looks and whispers rather than grand gestures. Their spoken delivery is always calm and measured, and when there is a later break from this and strong emotions are expressed, the effect is appropriately jolting.

The quiet approach also works for key supporting characters, notably Penny's doctor friend Miles, who crosses himself on first encountering the brothers without for a second breaking his cheery smile, and whose very gentle delivery nonetheless carries considerable dramatic weight. The tone of the film is always in tune with these performances, something that is occasionally disrupted by characters who are not working on this wavelength (the pushy lawyer, the camp party host, the drunken guest), so that we see them as Blake and Francis do, as outsiders to their world, threatening its delicate stability. The happy exception is their next door neighbour, a cheery preacher named Jesus (his "HEY ZEUS" number plate is one of my favourite humorous touches), who lives up to his namesake by being the only one who instantly accepts the two for who and what they are – when he insists on transporting Francis to the hospital and Blake reveals to him for the first time that they are conjoined twins, he says with barely a pause, "Then I guess you're going too!"

Despite watching it again three times on Metrodome's new UK DVD, I still have trouble pinpointing exactly what it is that makes Twin Falls Idaho so special. In the end its really down to a finely balanced combination of all the things that can be so wonderful about a small independent feature, where action is secondary to character, atmosphere takes precedence over pace, and originality is always prized over formula. And like so many fine independent films, this is about people rather than events, as genuinely touching a story of brotherly love as you'll ever see. As he drives the pair to hospital, neighbour Jesus describes them as "the biological representation of togetherness." Amen to that.

The UK DVD of Twin Falls Idaho has been along time coming, given that Sony's region 1 disc, whose anamorphic transfer was pretty damned good, was released six years ago. The transfer on this Metrodome region 2 disc appears to have been sourced from the same original, indicated by the occasional dust spots appearing in the same places, but in other respects the Metrodome disc has the edge over the Sony, with fewer compression artefacts and better levels of detail. Colour reproduction is very pleasing, nicely capturing the painterly compositions (the directors acknowledge the influence of both Vermeer and Edward Hopper). The running time suggests an NTSC to PAL transfer, but if that's the case then it's good one, with no obvious ghosting or contrast issues. Framing it 1.85:1 and the picture is anamorphically enhanced.

The Sony disc had both stereo 2.0 and surround 5.1 tracks – only the 5.1 track is on offer here, but that's fine, as differences between the two were minimal anyway. The rear speakers don't have much to say, but clarity is fine and there's some serious bass in the Halloween party sequence.

The only extra here was also the principal one on the Sony disc, a commentary by Mark and Michael Polish. As soft spoken here as they are on screen, there are moments when I momentarily mistook a comment on the action for off-screen dialogue. But it's all interesting stuff, covering the filming, the casting, the influences, working with actors, the tight shooting schedule (just 17 days) and a host of other aspects of the film. Particularly interesting is the information about their own performances, the rig that held them together, and the reaction of the other actors on seeing them in it for the first time (which is caught on camera – the actors got their first looks as their characters did).

The Sony disc also had brief biographies for Mark and Michael Polish and Michele Hicks, but their absence here is not an issue as the information is freely available on the net.

It's been a bit of a wait, but it's finally here on region 2 DVD. Many will have not seen or even heard of it (a few years has passed since its cinema release), but here's the opportunity to put that right. It's an unusual and remarkable debut, and one that has found its way onto one or two favourite film list, mine included. For the quality of the transfer, a worthwhile commentary, and a rather special little film, this disc is highly recommended.