LAS PEÑAS, 2009, SIERRA DE GREDOS

The car turned another bend, climbing higher into a land of sunscorched scrub, stunted trees and huge overhanging rocks. An arid landscape broken by sheer cliffs and sharp, boulder-strewn ridges. Stupefying heat. Galindez felt sweat soaking her shirt, trickling down her back. This had been the only vehicle left in the car pool, and now it had become an instrument of torture. Why no air conditioning? It was high summer, for God's sake. If she'd been a uniformed officer and not a lowly forensic scientist, they wouldn't have sent her out to the middle of nowhere in a vehicle without air conditioning. There was no point in complaining, she knew. No matter how reasonable the complaint, the same barrier always came up. The same look on their faces: Women – always complaining. Don't they realise? This is what keeps the pay cheque coming.

Galindez reached the crest of the hill and crossed a flat promontory leading to yet another steep winding road that curved around the flank of yet another ochre hillside. She slowed, seeing a small improvised shrine at the roadside a hundred metres ahead. Beyond the barrier, the sheer cliff fell into the valley far below. Tyre marks curved crazily from the centre line to the shattered gap in the wooden fence. Galindez drove slowly, taking in the profusion of cheap plastic toys, religious badges, a handmade cross and a portrait of Jesus, executed in luminous colours. Whoever ploughed through that barrier had friends with appalling taste.

A road sign: Las Peñas. Even the villages were named after rocks in this arid terrain. A two-hour drive in thirty degrees of heat. And waiting for her would be another heap of ancient bones. Another war grave. Joder. Why did they always send her? No one else available in Forensics, Ana María. Good practice for you, Dr Galindez. Do me a favour with this one, Ana? It's not far, just outside Madrid. She gripped the wheel, feeling a surge of resentment at what she was sure would be another wasted journey. In the mirror she saw beads of sweat on her face, the glint of her eyes behind the dark sunglasses. Her guardia ID swung gently on its chain from the sun visor, the small laminated photograph taken only a year ago: a picture of quiet confidence, her dark hair tied back, deep brown eyes bright with anticipation. Her name printed beneath the photo: Galindez, Ana María, Forensic Investigator. An image of her ideal self, calm and collected, just out of university with her doctorate, eager to start her career in the guardia civil. And this was how it had turned out. Collecting the remains of people killed in a war seventy-five years ago. Good going, Ana María.

It felt such a waste of time. All the years spent studying forensic science, developing skills of analysis and interpretation, peering at photographs of murders and suicides, learning the beguiling similarities between self-inflicted death and murder. Ways of avoiding the myriad opportunities to reach a wrong conclusion. All those skills focused on assembling a deeper truth. A truth no detective could ever piece together by observation alone. Time spent patiently gathering data. The hours of assiduous analysis devoted to identifying the logical sequence that would give up the secrets of a case. All the skills she'd acquired and yet so much of her time spent on these fruitless trips to recover the remains of people killed so long ago. Worse, Galindez knew she got these jobs because she was still the new girl. Last one in gets the shit jobs, they told her. Like that would make it better. Life's unfair – and then you die. Papá's colleagues said he'd had that phrase painted on his locker. He thought it was funny. But then he died and it really was unfair. She took a deep breath, reminding herself it was all good experience, that it would look good on her CV one day. One day.

She glanced at the map lying on the passenger seat next to the pieces of her satnav. Almost there. A faded road sign confirmed she'd reached her destination. A bleached and faded sign: Compañía Española de Minas, fundada 1898. The remains of an old stone wall hinted at what once might have been an entrance. Behind the wall, an ancient wire fence wound through the scorched grass. Several sections of fencing had collapsed, the folded strands of wire intertwined with the dry scrub swarming over the rusted fence posts. Near the wall were several old buildings. Two of the buildings were in ruins, walls folded crazily inward over their fallen roofs. The remaining buildings were clearly entering the final stages of disintegration. The entire place was steadily decomposing, sinking sullenly into the harsh terrain.

Cautiously, Galindez eased the car up a rough track running through the parched scrub and seared rocks of the hillside. Five hundred metres of uncomfortable driving ended at a wire fence where several cars huddled in the steaming heat. One, a green and white Lexus with the insignia of the guardia civil, its windows closed. Galindez was willing to bet they'd got air con in that. The dry ground crunched under the wheels as she pulled to a halt in a cloud of arid dust. Slipping her ID around her neck, Galindez collected her case and the canvas equipment bag and stepped out into the leaden heat of the sun.

It was worse than she'd expected. Heat prickled her scalp and she felt it begin to scorch her neck and arms – short sleeves didn't help but then she'd dressed for the office today, not knowing she would be packed off to an abandoned mine. Everything about this place was unpleasant: the sharp desiccated soil working its way into her shoes; the clammy feel of the damp shirt plastered to her back; the dazzling white light bleaching the surroundings, painful even through sunglasses. An uncomfortable but familiar start to her working day.

The gate in the fence creaked loudly. Ahead was the disused quarry, a semicircular gash carved sharply into the hillside. A careless array of abandoned, rusty mechanical equipment littered the quarry floor. On the steep hillside overlooking the quarry she saw an arched area of brickwork that must be sealing the entrance to the mine. A group of people were standing by it. The hot air shimmered, making it hard to see them clearly. As Galindez approached, she saw a man wearing the olive green uniform of the guardia civil. Closer now, Galindez saw a ragged opening had been smashed in the bricks. An opening so small it obliged those entering or leaving the mine to bend almost double. The man in uniform came towards her. Typical officer of the Benemérita: middle-aged, belly straining over the top of a thick belt, eyes obscured by large round sunglasses.

'Dr Galindez? Buenos dias. Teniente Molina. We spoke on the phone.'

'Holá. What have we got in there, Teniente?' She held out her hand. Molina ignored it.

'As far as I can tell, fifteen corpses. Skeletons, I should say. Very little left of them.'

'A killing from la Guerra Civil?'

'You tell me, that's your job. I just need cause and approximate date of death to finish the paperwork and put this to bed. You've done this sort of thing before, verdad?'

'I've done lots of cases like these, Teniente. They get monotonous after a while.'

He shrugged. 'Claro. That's police work, fifty-nine minutes of boredom and one of excitement an hour – if you're lucky.'

'Even so, I wonder why we bother. We catalogue them and then what? Nada. Usually there's no suspect and often no witnesses. Dios mio, it was seventy years ago. We aren't going to make arrests. God knows there's enough to keep us busy without digging up war graves three-quarters of a century old.'

'Maybe so, Dr Galindez. But in the guardia, orders are orders. Even for forenses like you. That's what keeps the pay cheque coming, no?'

'That's what they say,' she agreed. All the fucking time. We should have it on the badge.

Molina followed Galindez towards the mine entrance. A second guardia emerged, struggling from the hole in the brickwork. He saw Galindez and she felt the familiar sensation of being measured against that invisible benchmark her male colleagues carried around alongside their gun and their nightstick. Maybe it wouldn't be so annoying if they'd hide it a little. Especially since it was wasted on her anyway.

'This is Sargento Hernandez. Hernandez, Dr Galindez.'

The sargento gave her a cursory nod and stared at her chest. Clearly she met some of his criteria since he didn't even bother looking at her face. She folded her arms.

'You get back to the comisaría, sargento, I'll be along later,' Molina said. Hernandez took a last look at Galindez's breasts and walked back up to the cars parked by the fence.

Galindez looked at the ragged hole in the brickwork. 'Is it safe to go in?'

'Absolutamente. We've put up a couple of lights. You know, I think it shook the sargento when he saw what's in there.'

'I could tell he was the sensitive type.' Galindez took off her sunglasses, squinting against the white glare. She forced her way into the narrow gap, the broken bricks sharp against her back. Inside it was dark and the air smelled of earth. Molina followed, crawling awkwardly through the gap, panting from the exertion.

An electric lamp hung from a hook in the narrow passageway, throwing dull light along rough stone walls punctuated by the columns of bricks bearing the weight of the hillside above. Galindez's flashlight played over the dusty surfaces, a probing line of white light picking out rusty lanterns, heaps of broken tools and large coils of wire covered in lichen. Twenty metres in the passageway widened, ending in a brick wall with a heavy door fitted with a large rusty lock. There were storage spaces hacked from the rock on either side of the brickwork, most of the space occupied by piles of ancient equipment and tools, their form and function long erased by dust and cobwebs.

'That's the entrance to the mine,' Molina said, pointing to the door. 'But there's no key for the door and I don't fancy trying to force it open if we don't need to.'

Galindez nodded, her flashlight moving across upturned buckets, oil drums and wire netting. Dust flickered in the sharp beam. And there they were.

The killers must have piled the bodies on top of each other but time had changed the order of things. With the decomposition of the bodies, the skeletons had collapsed like a heap of firewood. Galindez knelt alongside them. She'd seen plenty of skulls in her short career yet she still felt there was a certain pathos looking into a face so denuded of its essential humanity. All that remained was this last unrecognisable vestige of its owner, the jaws open in the impossibly wide, astonished surprise of the long dead. Those where the jaw was still attached.

'From the look of it, none of these people died naturally, Teniente.'

Molina looked at the skull. 'That's a gunshot wound, isn't it?'

'Definitely. This is the entry point,' she pointed out a neatly drilled hole in the back of the head, 'and you can see the result here.' Turning the skull, she indicated the massive exit hole, a gaping expanse of the forehead missing. 'The bullet entered at the base of the skull, exiting through the forehead.'

'So what does that tell us?'

'Hombre,' Galindez smiled, 'someone shot him.'

Molina grunted humourlessly. He looked again at the dusty skeletons, so diminished in death, their essence long since drained away, the remains now crumbling slowly. 'There are no signs of identity.' He sounded disappointed. Galindez knew the feeling well.

She took latex gloves from her case and began to pull them on. 'I think it's best if I establish how many there are. Then we can get them bagged up.'

'There's no we.' Molina snorted. 'You get them bagged up. That's what you do, señorita.' He got to his feet and headed back along the tunnel to the entrance.

Galindez felt the cold starting to seep into her damp clothes. It wasn't unpleasant now, but after a while it would be. And she was going to be here quite a while, she was certain of that. She pulled off the gloves. There were things in her car she needed and it was pretty clear she wasn't going to get any help.

Galindez climbed back through the ragged hole in the bricks into the simmering white heat. The light was painful after the half light of the tunnel. Two people were standing outside the entrance. An old man holding a sheaf of papers, and a woman: middle-aged, short dark hair. Quite attractive, Galindez noticed. She wondered if they were relatives of the victims. That would be good: she could try for a DNA match. The thought cheered her.

Molina introduced them. 'Dr Galindez, may I present Profesora Ordoñez, professor of contemporary history at the University Complutense in Madrid and Señor Teodoro Byass, former manager at the Spanish Mining Company. Señor Byass tells me a large part of the mine and the neighbouring quarries closed after the Civil War.'

Señor Byass was clearly pleased to have had his retirement interrupted to give the history of this godforsaken hole carved into the barren hillside. 'As you say, Teniente, although we carried on some operations in the area until about 1970 – the year the company shut down. But the mine was sealed off long before that.'

'Before the war?' the professor asked.

'No, señora. It closed in 1953. I've got the papers here. I kept the files when the company folded. Here you are, señora.'

'It's señorita,' Ordoñez said, glancing at Galindez. 'But if we're being formal, I prefer profesora.'

Byass mumbled an apology as he handed Profesora Ordoñez the yellowed papers with their faded official stamps.

She examined them carefully. 'Had the seam run out?'

The old man shook his head. 'Orders from above. As you'll see in that letter.'

Profesora Ordoñez turned towards Galindez to read the letter. Her finger moved down the faded typewritten sheet. 'Orders from the General Directorate of Security, January fifteenth, 1953. For reasons of public safety ...' the Profesora skimmed the page, 'danger to passers-by, children and domestic animals ... immediate closure of the mine entrance ...'

'An order like that couldn't be ignored. Not back then,' Byass said. 'They sealed up the entrance within a few days.'

Profesora Ordoñez turned to put the papers in her bag and caught Galindez lightly with her elbow. 'I'm so sorry. Did I hurt you?' She squeezed Galindez's arm in gentle apology.

'No ha pasado nada, professor, my fault,' Galindez said, thinking it less of an accident and more an opening gambit.

Profesora Ordonez looked at the letter again. 'The letter is signed by the Military Governor of Madrid, General Antonio Valverde,' she read. 'As you say, Señor Byass, an order from the Capitán-General of Madrid wasn't something to be argued with.'

Molina sighed impatiently. 'None of that's important. As far as I'm concerned it's an open and shut case of a wartime killing. I'll leave you to do your job, Dr Galindez. I'm going to drive Señor Byass back to the village.'

'I may need some help,' Galindez protested. 'Those skeletons are going to fall apart once they're moved. If we could get a couple of officers in to assist, at least I could keep some of them intact. It would make the forensic investigation much easier.'

'A quick word,' Molina said, taking a couple of paces away from the profesora and Señor Byass.

Galindez followed him, knowing what was coming.

'Don't give me orders, Galindez,' Molina said in loud voice. 'You're just the cleaning woman here, as far as I'm concerned. You may have all day to spend on this but I don't. All I want is your report signed and dated and sent to the comisaría at Las Peñas by tomorrow morning. Get those bodies out of here and take them wherever the fuck it is you take them. And I want the hole in the bricks sealed up. I think I can trust you to arrange that, can't I?'