This is unlike anything else you’ll experience on the Fringe. It’s the kind of show you tell everyone about and certainly will not forget. Yet you probably won’t ‘enjoy’ it and it has one weakness. It’s an odd dichotomy.

Coma‘s creators Darkfield have been here before with previous site-specific pieces Seance and Flight. Their now familiar shipping containers take residence in Summerhall and provide the opportunity for truly immersive, unnerving, unique and innovative theatre. Their technology is astounding and features binaural sound, fed to audiences via headphones, to create an unparalleled sense of audio immersion.

As the audience wait to go in, there’s a palpable feeling of nervous anticipation among the assembled. There have been ominously loud noises from within and previous audiences filing out appear a little shell shocked. We are warned repeatedly that we will be lying down in the pitch black, in a claustrophobic environment – and once inside with the lights out – must not leave our position or try and move around.

On entering, the penetrating hum of white noise and automated instructions to lie down in the functional wood and plastic cramped triple bunk beds only adds to the sinister vibe. It hasn’t yet begun and already we’re immersed in another world. It feels like we’ve fallen into an episode of Black Mirror. The foreboding reaches crescendo as we are warned one last time, that this is the final opportunity to leave. It’s tempting. But we stay, the lights dim till the container reaches utter pitch-black, the claustrophobic sight of a low bunk looming above disappears and it’s too late to get out.

This isn’t the kind of pitch-black you get at night in the countryside. You can’t see your hand in front of your face. There are no illuminated exit signs or electronic red pin lights. The feeling of entrapment increases as we are informed we are now trapped in our own bodies.

It can become easy to feel overwhelmed with this combination of visual sensory deprivation and binaural audio immersion. As with all Darkfield’s creations, the effects are staggering. It genuinely sounds real and must be experienced to be fully understood. We believe there are people moving around with us, talking to us. There is some escape. Taking off the headphones briefly offers a slight reality check. But still, menacing white noise fills the container via speakers and the effects extend to movement and smells too – one of the latter lingers on your clothes for the rest of the day, ensuring you do not forget. As if you could.

There’s a problem though. The script we hear needs fleshing out and doesn’t carry enough impact. It must pique listeners interest, because lying in the dark, it is all we have.

Coma is totally inappropriate for those with any claustrophobia, tendency to panic or discomfort with the dark. It taps into those fears effectively.

While this may not be Darkfield’s best work so far in terms of the writing, they remain among the most fascinating and cutting edge theatre makers.