True darkness is something we rarely experience. It’s the stuff of spooky films and storybooks where nobody knows what lurks in the shadows or where your mind will wander. It’s this kind of mystery and confusion that Glen Neath and David Rosenberg (of UK immersive-theatre company Darkfield) are hoping you’ll experience with Coma – the third installment of their popular shipping-container productions – on at this year’s Garden of Unearthly Delights.

As with their previous shows Séance and Flight (which are also showing at the garden this year), Coma takes wary punters inside a pitch-black container, where darkness leads the mind to confusion, and even persuasion.

Outside, as sequined circus performers and magicians with megaphones whizz by, audiences lining up for Coma look somewhere between tense and excited as they – and I – await the coming darkness. We file into the confined space with trepidation, making our way to a bunk bed of our choice, as instructed by the speaker. The beds are stacked in three tiers, each hosting an uncomfortably rigid vinyl mattress. It feels as though we’re in a hospital, mental asylum or jail. It’s warm, and my skin sticks to the vinyl.

Once in our bunks, headphones go on as confused whispers between guests float through the room. Anxiety builds.

Before the lights go out, we’re instructed to consume something sitting at the side of our beds. Knowing not to take consumables from strangers, we all search around the room for confirmation that everyone will do it. We all agree.

The lights go out and the next half-hour makes clever use of the other senses – sound, smell and taste – to stretch the mind and allow the group to fall into a dream state together. This is where reality begins to bend, as sounds and spoken word come through the headphones, smells drift by, and the air moves (or does it?).

“The darkness is like another texture that surrounds you,” Rosenberg tells me, a few days earlier. “You become fairly susceptible to suggestion from the sounds, and there’s this doubt as to what’s happening around you.”

“We try to blur that moment where the audience doesn’t know what’s real and what isn’t,” adds Neath.

Are the whispers and chatter coming from your headphones or the container? Is there really someone inside the container, pacing between the bunks? Can you smell them? Did your friend cough? What is real and what is not? These are the questions whizzing through my brain as I navigate the total darkness before me.

Once the time is up, our dazed and confused bodies wobble out of the doors, grasping for words to share with our fellow guests. Nobody says a word to the punters eagerly awaiting entry. It’s as though there’s a collective decision that what happens inside, stays inside.

Neath and Rosenberg say this collective consciousness is an important element of their shows, and a result of the situational darkness especially. “The audience brings a lot to the shows,” Neath says. “Everybody has a different response because it’s such an extreme scenario to be in the complete dark.”

“When the lights go out, the space has gone as well,” Neath continues. “So you then try to recreate the space as a group. And once you’ve imagined the space, then what else can you imagine in the space?”

The concept of allowing the mind to wander and build its own narrative is a large part of the inspiration for Neath and Rosenberg, too. “We can really see how the imagination works in the audience and how they can create their own environment,” Rosenberg says.

It’s a stark contrast to the flashy, colourful, light-filled shows that grace the tents and stages throughout the garden. But it’s the immersive experience, void of sight, that leads the mind to create its very own show.

“There’s so much interest in anything that’s immersive these days ... but I think there’s something paradoxical about immersion. In fact, books are probably one of the most immersive art forms because it’s all about your imagination ... it’s not about being given everything all around you. For us, taking away vision for the audience, putting them into darkness and actually limiting some of their sensory input is the thing that creates a gap for the audience to fill in for themselves.”

Coma is showing at the Garden of Unearthly Delights until March 15. Tickets are available online