They Only Come at Night

If the mark of great theatre is that it changes the way you look at the world, then Slung Low might just be the greatest theatre company around.'They Only Come At Night' is like a half-hour adrenaline shot that leaves you with your heart racing, looking at everything around you with near-paranoid new eyes. The basic premise of the piece is a kind of walk-round, site-specific ghost train set in the underground car park of the Barbican. Given headphones and a head-torch you wander about, dimly aware that the show is about vampires and that you've just foolishly volunteered to let a theatre company try to scare you out of your wits.

What's fascinating is the way that the show makes you complicit in your own fear. Constant information overload through the headphones twinned with shapes lurking in the smoky shadows achieves a pretty acute sense of anxiety. We all know that vampires don't exist, but the fact that we allow ourselves to be frightened by the show feels like a kind of hyper-realised willing suspension of disbelief.In their programme notes, Slung Low note that in parts of the former Yugoslavia mothers prefer to tell their children that their fathers and older brothers were taken in the night by vampires than that they were murdered by someone who still lives in their town. In the same way, the vampires of visions don't need to be 'real'. At no point will someone wearing a cape and fangs leap out from the shadows. It is the shadows themselves that we should be frightened of.

'They Only Come at Night' succeeds precisely because it makes you look at the world through a prism of fear.That this sense of unease stays with you well after the show has finished, means that for a while you experience normal London as a terrifying alternate universe. Going home after the show, it felt like it might just be the most sensible way of experiencing the world these days. Perhaps we ought to be a bit more worried.