If anyone bought a ticket for tonight's show because of an advertisement, in which hundreds of coloured balls tumble gaily down a San Francisco hill, they may well have come ill-prepared. That ad's soundtrack was a cover version of Heartbeats, wherein José González (who, like the Knife, is Swedish) teased acoustic sunshine from an original that the electronic duo make more sinister than ever tonight.

The Knife have no interest in sunshine, nor in talking to their fans. Black balaclavas cover their faces, which are further obscured by a translucent black nylon screen, draped like a theatre curtain between them and us. Another screen hangs behind them, while projections of sad dolls and impossible matrices flicker across both, leaving the notoriously reclusive brother and sister ever more hidden in between. Papier-mache monsters with distorted heads and mechanical arms nod from dark corners of the stage.

Olof Dreijer uses assorted digital instruments to create a throbbing poignancy rarely found in computer melodies: sometimes it sounds like a robot blowing across the rims of bottles. Karin Dreijer Andersson's vocals are sharp, but not shrieking as on the record. She dances behind their stage veil to the chinking sounds of synthesised steel drums; it's a son et lumière ghost train, Jean-Michel Jarre for the ketamine generation. Even on the cheekier numbers from their last album, such as Pass This On, they bring out a menace more familiar from the new album Silent Shout, which ditches the pop for techno.

After just 40 minutes, the masked Scandinavian raiders disappear as mysteriously as they arrived. Yet, 15 minutes after that, some optimistic fans still stand and stare, hoping against hope that the stagehands dismantling the set are just another part of the performance.