WHAT are stories for? What is their purpose? What are their pleasures and perils?

These are the questions I have brought to the table today to ask the man and the woman sitting in front of me in the cafe of the Lighthouse in Glasgow, the city in which they live and work.

The woman is quiet, dark, French, an artist. The man – the writer – is the more vocal, intense but a man with a gulping laugh. They are partners in life and art. She is called Sandra, he is John, but they go under the name of Metaphrog.

They are storytellers, their chosen medium the graphic novel. They have won prizes for it, including being named Best Visual Artists in the Scottish Culture Awards by this very paper last year.

Their latest, The Little Mermaid, is the lushest thing they’ve done. It's a take on the Hans Christian Anderson fairy tale, the story of a mermaid who wants to be human. The Metaphrog version reinvents the tale as a swimmy, gorgeous vision of beauty and despair. Immersive, they hope, in every sense.

It is the product of eight or nine months of commitment. And that's just for the artwork.

"We worked for six days a week, long hours," explains John Chalmers. "And I think the time of investment in the making of it is slightly deceptive because Sandra has been working for 23 years, building on her skills and making something that we hope people will spend time in. Slow time, rather than just the superficial skimming over that our culture seems to encourage."

"I think I also like to explore new avenues," adds Sandra Marrs, her accent sweetly French-flavoured but, with a slight Irn Bru tang. "I'm not one of these artists who would just stick to the same way of doing things over a lifetime."

They have 20 years of joint work behind them and have managed to carve out a distinctive space for their strange, curious stories which on the surface can look childlike, simple even but, as The Little Mermaid proves once again, are full of hidden depths (sorry, in the circumstances it's impossible not to say it).

Despite first appearances, The Little Mermaid, they say, is not just for young adults. "We hope it's for people who love books," suggests Chalmers. "We asked the publisher to make it look like an art object.

"You're competing with naked people cooking on television to get their books out there and there's all these lavish packages ..."

Hold up. Naked people cooking on television?

"I think so."

I may have missed that programme, John.

"Don't try it at home."

There's probably a large risk element.

"Aye," says Chalmers laughing. "Chutney."

Anyway, fairy tales. When she was a little girl Marrs used to listen to the story of the little mermaid on record. "It just stayed with me forever. I think the sadness of it and the depth of feeling you get from it which you don't get from the Disney version for example – not that it's not a good movie adaptation – I think that's what is maybe so powerful."

There's a power to fairy tales, says Chalmers. "They still speak to us. They are often more filled with truth than the news.

"Quite a lot of them are about deeply human things like love and loss, unrequited love."

What for them is The Little Mermaid about then? "That sometimes your eyes can be bigger than your stomach," says Chalmers.

"Wanting to reach something that you can't reach and you can't have,” adds Marrs. “The little mermaid wants something that is not herself. She wants to be someone completely different. She's got a beautiful tail and yet she wants something else.

"I guess all young girls wish they were better looking than they are or someone else."

"Not just young girls but I think there's more pressure to be beautiful on young girls," agrees Chalmers. “Men and women aren't comfortable in our skins."

Let's rewind. Sandra Marrs was just 20 when she left France to travel to Scotland. She wanted to shake off her cultural baggage, find somewhere new. At a party in a flat in Govanhill she found John. "I was trying not to look at him because I thought I liked him," she recalls, smiling.

"I just remembered we got on quite well. I tried to speak French so she thought my name was Jean."

"I thought: 'That's a really weird name for a British person,'" Marrs adds.

They talked comics. They talked music. They had shared interests. Soon they were living and working together. Chalmers came from a scientific background (he has a PhD in Electronic and Electrical Engineering in Micromachining), but he had always wanted to write. He doesn't think the worlds of science and art are so different, really.

"I think engineers are much maligned. They have to apply a lot of imagination and originality, not just knowledge. They're quite creative."

He certainly wanted to be. "I never had the confidence. Meeting Sandra was the catalyst. It gave me the confidence to try.

"We realised that comics were quite complicated and we really enjoyed playing with that. It was great fun. When people said: 'Why aren't you using your PhD?' Or, 'You're wrecking your life,' we just thought we had purpose. And there's nothing better in life than being with somebody you love and having a purpose. You can't believe how happy that makes you."

Their first major project was Strange Weather Lately a wordy mixture of social realism and surrealism about, Chalmers says, "a lot of the things that bothered us – cheap drugs, low employment rates, unpleasant jobs that no longer gave people a human role, crappy consumer products."

Was that drawing on their own experience of that low-pay, dole-queue culture?

"Do you know, once we started working together we found a way,” Chalmers says. “We never had a washing machine. We don't have a car, we don't have kids. We just did it.

"We asked for sponsorship from the local community. So we got £50 from 10 people and that paid for the comic. We often had to count pennies."

"Out of the 20p jar," Marrs pitches in.

"But we really wanted to do it. I tutored."

"It was really precarious for years," adds Marrs, "but we were prepared for it.”

"It’s still precarious,” admits Chalmers.

"We had a romantic idea of the writer and artist," Marrs continues. "We knew we had to go through that period where we would struggle."

Giving up and giving in was never on the cards? "Quite the opposite," says Chalmers. They'd read Henry Miller and Knut Hamsun. They saw poverty as being part of the process. It was, they both admit, a very romantic vision.

"I think for me I had no choice," suggests Marrs. "This was what I wanted to do and taking a normal job would just have broken me, I think."

After Strange Weather Lately they created the Louis books, weird, strange little fables about globalisation and ecology that look like children's stories and yet have a deeper, darker undertow. I'm not surprised when Chalmers tells me his father died while they were working on one of them and that the grief fed into the story.

From there they started exploring the world of fairy tales, first with The Red Shoes and now The Little Mermaid. Familiar stories told in a distinctively Metaphrogian way.

Which brings us back to where we came in. Why do we need stories anyway, Sandra and John? Why do we need to revisit these old stories and tell them anew?

"Some people think that the purpose of stories was to let us know where there was food," says Chalmers. "I don't think it's as simple as that. I think people gathered together to hear stories not just to get warmth and shelter. They gathered together just to hear stories.

"I think it's an access to ourselves and others. I think it's one of the most important things. I think stories will be our salvation.

"It's about everything, the interconnectedness of everybody. There's a sense of recognition when you hear a good story."

Isn't there a danger it could be a crutch, a way to impose structure on the randomness of the universe? A way we delude ourselves?

"It's a comforting thing," agrees Marrs. "I think for a short while you are able to identify with characters and get into a zone where everything is true and wrapped up neatly at the end and has a logic to itself and is not going to be casting doubt on your life."

A consolation for the miseries of existence then? No, says Chalmers. There is much to be angry about; the war on the poor, environmental catastrophe. Even so, he says, "I think there is an innate joy in life. You get to hear The Fall. You get to hear The Smiths. You get to hear Country Joe and the Fish if you're lucky. You get a chance to listen to amazing things and read amazing things."

"Ultimately stories are food for the mind," adds Marrs. "It's the equivalent of eating for your brain. It would be really sad to not have that in your life, just a big emptiness."

What are stories for? Filling the void.

The Little Mermaid, by Metaphrog, is published by Papercutz.