Head concealed

I don't want to go on about this. But what is Abrahamson thinking by keeping the Fassbender head concealed?

"I know. Everybody is trying to get Michael in front of a camera," he says. "We have got Michael in front of a camera, and we cover him up. Actually, I love gambits like that. Casting Pat Shortt in Garage, a serious film, was a bit like that. What are you doing? But it's appealing to people because everybody wants to know how we're playing it. It becomes part of the story of the film."

He goes on to explain how Fassbender's physicality overpowers the disguise. By lighting the head in different ways, Abrahamson allows that apparently impassive globe to convey very different emotions. "It shows the power of the medium," he says.

It seems as if the writers of Frank liked Adam Paul, Abrahamson's bleak comedy about Dublin junkies, and made sure that their script got to the director. This makes sense. From what I've heard so far, Frank seems, like Abrahamson's debut, to straddle the frontier between the comic and the sinister.

John, played by Gleeson, finds himself part of an uneasy collective that makes a sound every bit as unusual as – many other comparisons are bandied around – those produced by the blues anarchist Captain Beefheart and the outsider troubadour Daniel Johnston. (Stephen Rennicks, another long-term collaborator, has been working hard on the music with the director.)

"Yeah, this is much more like Adam Paul than anything I have done since," Abrahamson says. "It doesn't quite have the bleakness of Adam Paul. It's a warmer film. One thing that I liked about Adam Paul, though, was that it moved from quite broad farce to something real and still felt like the same film. I think if people are moved by the film it will creep up on them. There is a continuity between the first two films and this."

It sounds as if Gleeson's character may be looking through the audience's eyes. He plays the relatively normal outsider who tries desperately to process the rampaging weirdness. As events progress, he develops an increasingly close relationship with the disturbed Frank and experiences ever greater hostility from Gyllenhaal's theremin virtuoso.

Sheltering in a Portakabin at the outer edges of the encampment, Gleeson muses on his apparent role as a stand-in for the paying punter. "I think so," he says. "He's a bit lost with the band for a while – which we will be also. There's a bit of crossover there. But the difficulty with being the eyes of the audience is that the character can disappear. But Lenny has been very careful about making sure that doesn't happen."

The conversation with Gleeson is perhaps the oddest part of an odd day. Recently seen in Joe Wright's version of Anna Karenina and James Marsh's fine Northern Irish thriller Shadow Dancer, Domhnall – son of Brendan, of course – is almost as head-spinningly busy as Fassbender.

He remains, however, unaffected and amiable. It's the voice that's disconcerting. Who's this English bloke? Gleeson has decided to stick with the accent between takes. The fact that he's nailed it so effectively makes the conversation even more peculiar.

"It's definitely not a character thing," he says, sweeping aside accusations of preciousness. "I have done it for the last few films, though. I did it for Shadow Dancer because I had heard so many bad Northern Irish accents. If you don't the vowels do start to come out." He laughs and swills some coffee. "It is a bit arsey, I know."

Culture shock

As Gleeson happily admits, the cast have undergone a fairly serious case of culture shock over the past few weeks. Shooting on Frank began in New Mexico and then speedily moved to this overpoweringly gorgeous, bracingly damp corner of Ireland. The home country plays itself and England. Albuquerque stands in for Austin. Abrahamson could hardly have induced a greater jolt if he'd dragged the poor souls from Kinshasa to Vladivostok.

Still, Gyllenhaal appears to be bearing up quite nicely. She refuses to complain. She misses the chance to make any diva noises. How disappointing.

"It's been good but wild," she agrees. "All of a sudden we're here and there are different characters, weird accents, Guinness. Ha ha! You could not experience greater differences in terrain. From dry, dry sun to wet, wet cloudiness, and those things really affect the experience. And, of course, it's such a very weird movie. It's so unusual."

Which brings us back where we started. Whatever else happens with Frank, even the most unforgiving observer would have to admit that Abrahamson and his team are not afraid of edging into fresh, unexpected, weird territory. We will, most likely, have to wait some time before the picture emerges. Guiney is cautious about discussing release dates, but no official sighting of the head is likely before the end of the year. Wave goodbye until the seasons close in once more.

Darkness looms and we trundle our way back up the precarious path towards the relative normality of rural Wicklow. Leaving Shangri-La must have been a little like this. If Shangri-La had proper catering.

to be continued...