Audience, Soho Theatre, London

This Edinburgh Festival hit is not so much a show as an initiation. And to give away its secrets would be, if not sacrilegious, at least unfair. Belgian theatre company Ontroerend Goed blur the distinction between actors and audience, between theatre and life, in a show with no clear beginning and end. At what point do we become “the audience”? When we enter the auditorium? When we leave our coats? And when does the performance begin – with the official announcement to switch off our mobile phones?

An actress steps up, pedantically explaining how to behave, when to applaud. This is a conceptual joke, as Ontroerend Goed then proceed to violate the unspoken rules of engagement and trust between players and playgoers. Are you safe in the dark, or will the camera be turned on you at any moment?

We are bombarded with “statistics” about ourselves, possibly invented. “Forty-five of you came in alone. There is one group of four. Six of you are fat – you know who you are.” A warm-up man establishes a friendly rapport. Then the infamous moment comes where a camera is trained on a “random” audience member. Actually, it’s always a young woman, who is invited, with a bullying chant, to “spread your legs, spread your legs”. There are walkouts and cries of “This is bullshit!” and “Move on, mate, this isn’t working,” and the MC assures us that all is going to plan, that we did the right thing and stood up for her. Then an actor in the audience jumps up to add “but 11 people laughed”.

From this point on the audience is tense, watchful, aware that any reaction could create a judgment. An actor delivers a passionate speech about the power of humanity. We are bombarded with coercive rap. To join in or not to join are both decisions freighted with meaning, as the clips of fascist marches, football riots and political uprisings underline. Despite the apparent anarchy, it’s a fairly tight show, moving rapidly through discrete scenes. And there’s no clear moment when our interaction with the actors finishes.

I spot the young woman in the bar downstairs and ask her whether she’s a plant. She assures me she isn’t and explains that it was upsetting to be picked on, but that she trusted the actor not to take things too far. Like the performers, she has a slight accent and I’m still not convinced it wasn’t a set up.

It’s a brave group of actors who can set out so thoroughly to invite contempt. I’ve never felt so uncomfortable and on edge in a theatre, and this funny, but also frightening show will stay with me for a long time.

www.sohotheatre.com