There is something about disturbing neighbours that makes them a morbidly interesting subject for horror movies. Apart from, to quote just a couple of examples, Roman Polanski’s Rosemary’s Baby, Michael Haneke’s Funny Games, and Woody Allen’s comedic take on the genre, Manhattan Murder Mystery, there is also the Spanish Para Entrar a Vivir, by Juame Balaguerò, which was presented at the Venice Film Festival in 2006 as the pilot episode of a series of made-for-TV horror movies, broadcast last year in the UK. Perhaps part of the fascination with this subject, at least for us city dwellers, lies in the fact that we are all familiar with the apparently petty and yet deeply upsetting consequences of living next to, underneath or above someone who is loud, rude, or just somehow weird. In other words, we admit or at least contemplate the plausibility of the crazy neighbour we try to avoid forcing his way into our lives and taking control, torturing or ruining us.

Juan Mayorga’s Nocturnal, first produced in Spain in 2004 and now presented at the Gate Theatre in a translation by David Johnston, has very much to do with the disturbing-neighbour horror topos, but it would be superficial to take it simply as a comment on how dangerous it can be to have a sociopathic man living in the flat upstairs. When the sociopath in question, identified only as Short Man (Paul Hunter), enters the bar where the Tall Man from the flat downstairs (Justin Salinger) is relaxing, they don’t know each other - or they do, but only as ‘two shadows [who] pass each other on the stairs every morning’. What is going to transform this relationship completely is not so much the fact that Short Man wants to be friends with Tall Man, nor the fact that Tall Man doesn’t feel the same. It’s something called ‘Section 3754’ - or, the Immigration Act. While the content of this is not made explicit, we understand that it gives any citizen the power to turn in any person whom he or she believes to be a foreigner without legal papers, no questions asked. A simple new law is giving Short Man the power to ask, or rather demand, whichever favours he wants from Tall Man - and all he wants is a bit of friendship: ‘I’m not going to make you work for me or commit a crime or lay a finger on you. One day, I might ask for a bit of conversation, the next go for a walk with me. Nothing terrible, nothing degrading’.

Except, of course, this itself is deeply degrading. It is degrading for someone as cultured, well-read and clever as Tall Man to be working the night shifts in a decrepit hospice. It is degrading to be forced to live in a miserable apartment with his lovely translator wife (Justine Mitchell) who is getting more and more tired of the situation. It is, more than anything, degrading to have no choice but becoming friends with such a mediocre, unpleasant man as Short Man. Obsessed with not being ordinary, the latter has spent the last couple of decades trying to educate his ordinary, sleepless wife (Amanda Lawrence, arguably the best-cast and most satisfyingly frustrated performer of the evening), uselessly attempting to convince her to read more novels and watch less television and stop following that idiotic programme about insomnia in the early hours of the morning - the strange, Jeremy-Kylesque stories of its callers fill in the spaces between scenes, projected on a small screen next to the stage. And now the Short Man wants someone to educate him, to be his mentor, someone to look up to; how apt that his mentor should also be his slave - power, here, is not about merit, but about privilege, and possibly luck. Some people are born to live in the sun and work day shifts, and some people are nocturnal animals, by nature and weakness, because of their inability to sleep, or, perhaps more cruelly, by passport circumstances.

The four characters cross and reflect each other; as the play develops, the force relations between them are refracted and echoed in all possible directions. Everyone reveals cracks and ambiguities: Short Man, whom we spend most of the play disliking, does have a much nicer, caring side that pushes him to take charge of all the repairing needed in the building - or is that just another attempt at almighty control? His wife is submissive and fearful and unfriendly - yet she fondly remembers the little village of their honeymoon. Whereas the wife of Tall Man distracts him by teasing him with funny stories of imaginary (or maybe not) men who pursue her in the street. In a particularly well-devised scene, the two couples, each in their own living room, share the stage, roughly divided by light in two overlapping halves: Lyndsey Turner’s direction is showing us their absurd effort to pretend that the other two do not exist, that they are only the source of an occasional night disturbance, that each of them is safe and isolated inside the tiny box of their respective flats. That their lives move in parallel lines, physically close but destined, in theory, never to touch. And when the lines are overstepped and honesty finally makes an entrance in the relationships between each husband and each wife, the outcome is not what we might have expected.

Mayorga’s play will resound particularly with people who have lived in another country and been forced to deal with the local bureaucracy; all those who have had to be kind and obedient, even in response to incompetence or stupidity, in order not to jeopardise their chances of keeping their home, their job, or even their right to remain where they are. If what makes horror movies scary is the plausibility of the situations they present, or the possibility of imagining to be in the position of the person who is being attacked by a monster or enslaved by an evil man, then this play is quite similar to a horror movie. In February, the government of the country in which I was born and brought up, a fully democratic country that is part of the European Union, passed a law that allows doctors to overlook their obligation to privacy and thus turn in illegal immigrants who come looking for medical treatment. It is now easier than ever to imagine a decent, educated man being ‘at the beck and call of just anyone’ simply because of a little twist of fate.

Till 16 May 2009