Art: Are you seeing double yet?

Jane and Louise Wilson Serpentine Gallery, London

To say that the work of Jane and Louise Wilson, the identical twins shortlisted for this year's Turner Prize, is about moving pictures is not as banal an observation as it might sound. Among the many (possibly too many) things that the Wilsons concern themselves with are: the tension between images that move and images that do not; the expectations we have as viewers of video as a medium; some kind of collective folk-memory of movies and television; very possibly, the technical arcana of transferring film to video and video to laser-disc; and a host of other filmic things currently slipping and sliding their way around the walls of the Serpentine Gallery in what is being sold as the Wilsons' first-ever survey exhibition.

That it is difficult to know where to start at the this show should probably be seen as some kind of triumph of the sisters' art. One thing that all of the works in the exhibition have in common is a preoccupation with the way in which architecture imposes movement. When you walk into the gallery, you are faced with what looks suspiciously like the door display at your local B&Q: charmless fire-doors, pseudo-Georgian chipboard doors, doors with brass handles and so on, all arranged in an installational centrepiece.

Around these hang still photographs of, well, doors: the door to a committee room in the House of Commons; another to the parliamentary press gallery; a whole corridorful of doors at an abandoned secret-police prison in East Berlin. These have the strange effect of both seducing and repelling at the same time: repelling, because the associations of the specific buildings are those of power and threat; and seducing, because half-open doors - blame Freud or Pavlov here - demand to be walked through.

Since you can't, you do the next best thing and walk instead into one of the three installations the Wilsons have placed in the Serpentine's nether half. Having lured you there by playing on the confusion between the gallery's actual architecture and the architectural images which hang on its walls, the sisters now introduce the element of motion.

All three installations involve multiple videos projected upon several walls, which, absolutely intentionally, makes it impossible to see any of the works in their entirety at any one time. Not only does this defy the normal architectural agenda of art galleries, it also suggests some kind of collusion between the images projected on the Serpentine's walls and the walls on to which those images have been projected. Perhaps it's a sideways swipe at the whole idea of institutions and the establishments that build them, a half-seen glimpse of the Serpentine Gallery as an artistic Stasi HQ.

What makes this bravura act of ingratitude particularly breathtaking is the knowing way in which the Wilsons handle their medium. Just when you feel you're about to get a grip on whatever it is that they're about - pen poised above notebook, if you're a critic - the sisters' pictures move briskly on to something else (the kaleidoscopic running-together of parliamentary carpet patterns, say), suggesting some kind of narrative and then instantly denying it.

At the same time, the Wilsons are also busy saying that none of this should worry you, really: films are, after all, just films. In Parliament (A Third House) (1999), the fetishised clopping of the projectors and their red, blue and green lights are purposely included as part of the work, just to reassure us that we're in familiar territory. In Stasi City (1997), the film's prettily filtered setting - all brown leather padding and wood-grained floorboards - draws us back to the cosiness of television circa 1970. The elfin figure - a twin - who levitates down the empty corridors of power does so in the nostalgic manner and dress of an episode of The Prisoner.

In the centenary of his birth, the most obvious reference in the Wilsons' work is, not unaptly, to Alfred Hitchcock. At the centre of all of their films is absence: of the Stasi in Stasi City, of the American Air Force in Gamma (1999), shot at the abandoned US nuclear base at Greenham Common. This absence is emphasised by the occasional momentary irruption into the works of the twins themselves, seen dressed in gas masks or pushing their way through a set of revolving doors, or jokily represented next to an Air Force sign that reads "Two man policy, no lone zone". These Hitchcockian vignettes clearly reinforce the central drama of the Wilsons' films, but they also invite the viewer to see them as movies. The question you might care to ask yourself is: why?

The answer, I suppose, is to tease the viewer, to ask him to look at the works in one way and then to suggest that he should really have been looking at them in another. See the Wilsons' films as three-dimensional and they will perversely insist that they are two; watch them as movies and their static, decorative quality becomes inarguably apparent; see them even as film and they will ask you whether they should not more properly be viewed as architecture.

Most slippery of all, consider them on what would seem to be their most obvious level - for example, as a haunting commentary on political power - and they will straightaway protest that they are actually all about prettiness. The image you take away of Hohenschoenhausen prison is not of abandoned torture chambers but of a corridor of choreographically opened doors which reveal patterns of light in the manner of Busby Berkeley; that of Greenham Common, the Hollywood glamour of military architecture.

In the end, you may choose to read all this in one of two ways. Either the Wilsons are saying something sharp and elusive about the trivialising effect of film as a medium; or they are scampering, clever and naughty, through things that arguably deserve a less facile treatment. Decide for yourselves.

Jane and Louise Wilson: Serpentine, W2 (0171 402 6075), to 31 October