When viewing Dawn Mellor's grotesque celebrity portraits, it helps to know that the artist once worked as an S&M cabaret performer. These images, arranged in a repulsive, hilarious rogues' gallery, are riddled with cruelty, sex and power - all distorted into nightmarish, horror-film visions. To give you some idea of the sadistic tinge to the work, Michael Jackson is represented in his Thriller video manifestation, with bulging red gobstopper eyes and zombie pallor - and he looks among the healthiest, most well-adjusted here.

Mellor's tone ranges from the poisonous - Cherie Booth, sporting red and black lingerie and a black penis, writhes in ecstasy with her hands in two skulls - to the oddly tender. Portraits of Virginia Woolf (holding a key), Beth Ditto (resting on carrots) and Judy Garland (with two faces, public and private) are as kind as the rest are savage. Hillary Clinton appears to be unzipping a face mask, Pope John Paul II, surrounded by hovering penises, reads a note saying: "I like boys too." Madonna is trussed up in bondage gear, her identity hidden.

Grouped together, these images revel in the way celebrities present themselves, but also how hungrily we feed on that. There is a voodoo power at work: you feel attracted and repulsed, but cannot break the cycle, cannot stop looking. Before you pull away from Mellor's work in horror, it deftly reminds you that we are all complicit in making these monsters, and keeping the ghastly images of them alive.

· Until May 3 2008. Details: 01392 431786.