When I walked down the Duke of York Steps to the ICA, the assembled men in uniform posing for photographers looked like an emergency anti-bomb squad. But they turned out to include real-life street rangers, nightclub bouncers and, in the centre, the chief beadle from the beadles of Piccadilly's Burlington Arcade, the oldest and smallest police force in the world.
Once inside, this motley group began patrolling the "Beck's Futures 2004" exhibition. Nicoline van Harskamp, one of the artists shortlisted for the munificent £65,000 of awards, has hired a regularly changing force of guards, whose presence generates a mood of brittle unease in the gallery. On one level, they resembled entertainers rather than professional heavies, and on another they reminded me of the increasing emphasis on surveillance throughout the capital.
Wisely, van Harskamp has asked them to behave in a normal way, resisting any temptation to pretend that they are "living sculpture" in a performance piece. Her comprehensive research, published in a sober booklet called Guide to London Guards, shows just how many different kinds of "street supervisors" now police the city. Whether private or public, they embrace everything from retail security vigilance to Salvation Army soldiering. Van Harskamp points out the increasing need for high visibility. "Especially since September 2001," she writes, "fluorescent yellow has been ingrained in the London streetscape." Even so, her work makes us aware of the tension between visual illusions of power and the guards' limited effectiveness.
Through her well-judged blend of documentary sobriety and theatrical flair, van Harskamp stands out in the 2004 line-up. Yet the unsettling aspect of her work chimes, in different ways, with the contributions by other exhibitors. Tonico Lemos Auad's animal images are sculpted from the fluff of a carpet specially laid in a first-floor gallery. From a distance, these small, low-lying cats and squirrels look inconsequential. But the blurred forms turn out to possess a surprising vulnerability. Auad gets the fluff by scraping with a surgical scalpel, so the animals are surrounded by evidence of violent activity. Their lack of clear definition has a spectral quality. Some have lost limbs or heads, while in one corner a detached tail lies marooned.
Auad is fascinated, above all, by fragility. In the same room, he displays bunches of bananas pinpricked with the outlines of human faces. Near-invisible at first, they gradually become clear as the banana skins decompose, causing the drawings to oxidise into blackened marks. Long before the show ends, they will all have perished. And even if the fluff animals survive the visitors' urge to touch, stroke or prod them, they can't be expected to last half as long as sturdier art objects.
Throughout this eerie exhibition, the feeling of frailty and isolation is inescapable. Imogen Stidworthy's film installation focuses on two Cilla Black impersonators, both singing her Burt Bacharach hit Anyone Who Had a Heart. Fascinated by Cilla's childhood memory of practising her songs in an empty upstairs room at home, Stidworthy recorded the impersonators in a spooky anechoic chamber. Resisting acoustic elaboration, it defeats their attempts to project their voices and bring Cilla to life, giving the films a manic and macabre quality.
In this respect, Stidworthy's work has links with Susan Philipsz's nearby audio piece. With one finger, she plays a piano version of the chilling theme tune from Nicolas Roeg's film Don't Look Now. The notes assume an even more elegiac quality when accompanied by Philipsz's looped silent film Returning, showing a Berlin park where people either pause to stare at the Karl Liebknecht Memorial or, more often, wander past without a glance. The monument, paying tribute to the revolutionary leader murdered for his beliefs along with Rosa Luxemburg, is shot in such a shadowy way that it scarcely appears significant. But Philipsz insists on remembering Liebknecht - in another audio piece, she sings a desolate Irish lament for "the lass of Aughrim", taken from James Joyce's story "The Dead".
Saskia Olde Wolbers, born in Holland and now based in London like so many foreign artists of her generation, presents a claustrophobic video installation set in an imaginary hospital. At once clinical and dreamlike, Interloper is based on the true story of a mentally ill Frenchman who pretended he was a doctor. Comatose in intensive care, he levitates from his bed and glides through the building's polished, metallic and desolate interstices. Despite its origins in reality, Interloper veers between the clarity of Wolbers's carefully crafted stage sets and an elusive place where floating shapes endlessly melt and reform.
Elusiveness is the leitmotif of the entire show. Ergin Cavusoglu, a Turkish artist born in Bulgaria, trains his video camera on the Bosphorus Straits at night. The shadowy vessels silently moving along the river, whose banks divide Istanbul, may contain all kinds of illicit and dangerous cargo. Because the men steering these anonymous ships remain unaware of the artist's lens, Cavusoglu takes on the identity of a security surveillance operator or a mysterious watcher, subjecting everything around him to a voyeuristic gaze.
Another exhibitor, Andrew Cross, takes his camera to the Cascade Mountains near Seattle. But instead of celebrating the sublime, epic grandeur of the countryside, he concentrates on filming the mouth of the longest train tunnel in America. We watch with him, waiting for a locomotive to erupt from the darkness. Although smoke seeps from the tunnel, only a distant and unidentifiable sound can be heard. Cross calls the three-part work Foreign Power, suggesting an imminent invasion. And the sense of expectancy he creates in each sinister sequence becomes almost unendurable by the end.
"Beck's Futures 2004" is at the Institute of Contemporary Arts, London SW1 (020 7930 0493) until 16 May