It just shows what you can do with next to nothing. Conor McFeely's Ink Mathematics is an installation of torn paper and tube lights that, at first sight, look as if they've been scattered around the gallery walls and floors willy-nilly. Believe it or not, it's a great achievement to make an exhibition look as if it has just been dumped there.

Such seemingly arbitrary composition is actually the result of painstaking artifice. You can tell because it gives you the creeps. It looks odd, awkward, something other than art as you know it. Maybe it's not art at all, but, like the innovative sculptural scrapwork of Joseph Beuys, a form of affective magic.

But, unlike Beuys's eco-shamanism, McFeely's perverse brand of hocus-pocus appears to be up to no good. The brief statement on the gallery wall claims that the work "explores the related subjects of fire and arson... the state of arousal sparked by them".

McFeely's materials are perspex, thermoplastic, ultraviolet, black lights, bundles of firelighters and rolls of paper treated with invisible ink. The light is not the light of this world. It bleaches everything out, turns everything negative.

The scrappiness and sparseness of the assembled objects give extraordinary, evocative significance to the occasional fragments of anonymous texts. Next to a photocopied image of a moonlit doorway and amid a pile of screwed-up paper embedded in spills of dried plaster, we read: "I am made out of water. You wouldn't know it, because I have it bound in... Not only do we have to walk around without being absorbed by the ground but we also have to earn our livings."

So what is McFeely up to? Is he some kind of displaced anarchist-electrician? A 21st-century electro-alchemist? Common sense is slipping away, serendipitous signs are everywhere and the ordinary world is ready to explode. McFeely's just an artist, but he's a good one.

Until January 7. Details: 0114-278 2600.