She knows she should fetch someone. Or at least tell Shelagh, her best friend, who is the deputy on the dig. Alice is not a trained archaeologist, just a volunteer spending some of her summer holiday doing something worthwhile. But it’s her last full day on site and she wants to prove herself. If she goes back down to the main camp now and admits she’s on to something, everybody will want to be involved, and it will no longer be her discovery.

In the days and weeks to come, Alice will look back to this moment. She will remember the quality of the light, the metallic taste of blood and dust in her mouth, and wonder at how different things might have been had she made the choice to go and not to stay. If she had played by the rules.

She drains the last drop of water from the bottle and tosses it into her rucksack. For the next hour or so, as the sun climbs higher in the sky and the temperature rises, Alice carries on working. The only sounds are the scrape of metal on rock, the whine of insects and the occasional buzz of a light aircraft in the distance. She can feel beads of sweat on her upper lip and between her breasts, but she keeps going until, finally, the gap underneath the boulder is big enough for her to slide in her hand.

Alice kneels down on the ground and leans her cheek and shoulder against the rock for support. Then, with a flutter of excitement, she pushes her fingers deep into the dark, blind earth. Straight away, she knows her instincts are right and that she’s got something worth finding. It is smooth and slimy to the touch, metal not stone. Grasping it firmly and telling herself not to expect too much, slowly, slowly she eases the object out into the light. The earth seems to shudder, reluctant to give up its treasure.

The rich, cloying smell of wet soil fills her nose and throat, although she barely notices. She is already lost in the past, captivated by the piece of history she cradles in the palms of her hands. It is a heavy, round buckle, speckled black and green with age and from its long burial. Alice rubs at it with her fingers and smiles as the silver and copper detail starts to reveal itself underneath the dirt. At first glance, it looks to be medieval too, the sort of buckle used to fasten a cloak or robe. She’s seen something like it before.

She knows the danger of jumping to conclusions or of being seduced by first impressions, yet she can’t resist imagining its owner, long dead now, who might have walked these paths. A stranger whose story she has yet to learn.

The connection is so strong and Alice is so absorbed that she doesn’t notice the boulder shifting on its base. Then something, some sixth sense, makes her look up. For a split second, the world seems to hang suspended, out of space, out of time. She is mesmerised by the ancient slab of stone as it sways and tilts, and then gracefully begins to fall towards her.

At the very last moment, the light fractures. The spell is broken. Alice throws herself out of the way, half tumbling, half slithering sideways, just in time to avoid being crushed. The boulder hits the ground with a dull thud, sending up a cloud of pale brown dust, then rolls over and over, as if in slow motion, until it comes to rest further down the mountain.

Alice clutches desperately at the bushes and scrub to stop herself slipping any further. For a moment she lies sprawled in the dirt, dizzy and disorientated. As it sinks in how very close she came to being crushed, she turns cold. Too close for comfort, she thinks. She takes a deep breath. Waits for the world to stop spinning.

Gradually, the pounding in her head dies away. The sickness in her stomach settles and everything starts to return to normal, enough for her to sit up and take stock. Her knees are grazed and streaked with blood and she’s knocked her wrist where she landed awkwardly, still clutching the buckle in her hand to protect it, but basically she’s escaped with no more than a few cuts and bruises. I’m not hurt.

She gets to her feet and dusts herself down, feeling a total idiot. She can’t believe she made such a basic mistake as not securing the boulder. Now Alice looks down to the main campsite below. She’s amazed – and relieved – that nobody in the camp seems to have seen or heard anything. She raises her hand, is about to call out to attract someone’s attention when she notices that there’s a narrow opening visible in the side of the mountain where the boulder had been standing. Like a doorway cut into the rock.

It’s said these mountains are riddled with hidden passages and caves, so she’s not surprised. And yet, Alice thinks, somehow, she knew the doorway was there, although there’s no way of telling from the outside. She knew. Guessed, more like, she tells herself.

She hesitates. Alice knows she should get somebody to come with her. It is stupid, possibly even dangerous, to go in on her own without any sort of back-up. She knows all the things that can go wrong. But she shouldn’t have been up here working on her own anyway. Shelagh doesn’t know. And besides, something is drawing her in. It feels personal. It’s her discovery.

Alice tells herself there’s no sense disturbing them all, getting their hopes up, for no reason. If there is anything worth investigating, she’ll tell someone then. She won’t do anything. She just wants to look.

I’ll only be a minute.

She climbs back up. There is a deep depression in the ground at the mouth of the cave, where the stone had stood guard. The damp earth is alive with the frantic writhing of worms and beetles exposed suddenly to the light and heat after so long. Her cap lies on the ground where it fell. Her trowel is there too, just where she left it.

Alice peers into the darkness. The opening is no more than five feet high and about three feet wide and the edges are irregular and rough. It seems to be natural rather than man-made, although when she runs her fingers up and down the rock, she finds curiously smooth patches where the boulder rested.

Slowly, her eyes become accustomed to the gloom. Velvet black gives way to charcoal grey and she sees that she is looking into a long, narrow tunnel. She feels the short hairs rise on the back of her neck, as if to warn her that there is something lurking in the darkness that would be better left undisturbed. But that’s just a childish superstition and she brushes the feeling away. Alice doesn’t believe in ghosts or premonitions.

Squeezing the buckle tightly in her hand, like a talisman, she takes a deep breath and steps forward into the passageway. Straight away, the smell of long-hidden, subterranean air envelops her, filling her mouth and throat and lungs. It’s cool and damp, not the dry, poisonous gases of a sealed cave she’s been warned about, so she guesses there must be some source of fresh air. But, just in case, she rummages in the pockets of her cut-offs until she finds her lighter. She flicks it open and holds it up to the dark, double-checking that there is oxygen. The flame gutters in a breath of wind, but it does not go out.

Feeling nervous and slightly guilty, Alice wraps the buckle in a handkerchief and pushes it into her pocket, then cautiously steps forward. The light from the flame is weak, but it illuminates the path immediately in front of her, throwing shadows on the jagged grey walls.

As she moves further in, she feels the chill air curl around her bare legs and arms like a cat. She is walking downhill. She can feel the ground sloping away beneath her feet, uneven and gritty. The scrunch of the stones and gravel is loud in the confined, hushed space. She is aware of the daylight getting fainter and fainter at her back, the further and deeper she goes.

Abruptly, she does not want to go on. She does not want to be here at all. Yet there is something inevitable about it, something that is drawing her deeper into the belly of the mountain.