Some punters are already laying bets that Hayley Willis's debut album, Come Get Some, will scoop the 2004 Mercury music prize. That's probably the kiss of death but it does reveal a groundswell of support for someone whose public profile is practically subterranean. Inside the tiny Spitz, record industry types are everywhere. "Thanks for coming. Thanks for not paying," quips Willis.

Willis should not have to wait long for paying customers, though. She has both a raw, quivering intensity and admirable versatility. On The State Within she channels the New Orleans blues voodoo of Dr John, while elsewhere she evokes Fairport Convention's folk-rock. She resembles Beth Gibbons in having an eldritch charisma that evaporates the second the music stops. Her deep, smoky singing voice and high, quiet speaking voice seem to come from different people.

But Hayley Willis is not alone onstage. There's a smartly dressed guitarist who might have stepped out of the Tindersticks, a bassist in a Linkin Park-like wool hat and, it seems, one of the Fabulous Furry Freak Brothers on drums. Wobbling his head in a huge cloud of hair, he looks as if he's about to produce a spliff of titanic proportions. He also looks like he's drumming in a trance, his whole body rippling.

At one point the guitarist breaks a string. While he's fixing it, Willis asks the crowd for requests and agrees to a quick version of Dolly Parton's Jolene. It's an eerie, sinuous rendition, full of creeping dread.

The other cover version is planned. Cameo's funk perennial Word Up is stripped down to a feverishly sensual piece of 3am blues that banishes all memories of Larry Blackmon's codpiece. Like everything Willis delivers tonight, it's mesmerising.