It was technically spring, if you took notice of groundhogs and almanacs that marked the seasons according to exact dates, but it was still bitterly cold in rural Gloucestershire. Martin Garvan left the comfort of his heated Range Rover only reluctantly and set off up the unmarked path towards the place where his sheep grazed. At least two of them were close to giving birth. He needed to bring them back to the farm and keep an eye on them. The trailer on the back of the car was prepared for the task.

It was past dawn, but the sky was still miserably grey and a low mist covered the ground. This was a long way from the view of shepherding espoused by the Romantic poets and the even more idealistic landscape artists of a couple of centuries back. It was hard, cold and muddy work.

As he neared the top of the slope he started to wonder exactly where his sheep were. This was, despite a chill wind that made him pull his collar up, the leeside of the hill. They ought to be hunkered down by the drystone walls or in the wooden shelters dotted about the hill to provide a warm place for sheep going into early labour.

He couldn’t see them anywhere.

What he did see was something that shouldn’t have been there, that had certainly not been there before.

Not the ancient Barrow, of course. The low wall around it kept the sheep out as long as the tourist shut the gates, and his only interest had been when the university asked permission to use some of his grazing land as a camp site for a few weeks while they did a survey of it. The tents where they were still sleeping and those erected over the place where they had been digging loomed silently in the mist. He had given them permission for all of that.

But he didn’t give them permission to build anything.

“What the bloody hell are these?” he asked himself as he approached the ring of stones. He had made a bet with himself that they would be made of fibreglass or some such artificial substance. Maybe some group of druids planned on doing something silly. Or maybe it was the BBC. If it was the former he’d chase them off. If the latter, they owed him an apology and compensation for messing up his land.

A lot of compensation. He was a licence payer, after all. Time he got some of it back.

He reached out and touched one of them. He was surprised to find that it really was stone. It felt like stone. When he pushed against it, he felt the heaviness of a huge slab that had to have been put in place with a crane.

Then he felt a tingle that started in his hand against the stone and travelled up his arm. It was like an electric shock but not quite so painful.

Even so, he screamed as his vision blurred and he felt as if his feet were no longer touching the ground.

Moments later, still screaming, he looked around in full sunlight at a hill that was both familiar and unfamiliar to him. The Barrow was there, though it looked different – newer, somehow, as if it had just been finished. The grass was only just growing over the mound along with the sort of wild flowers that took hold whenever soil was disturbed.

The stones were gone. He was standing in an untouched meadow with nothing else in sight.

Most of his sheep were there. They seemed to be all right. They were grazing perfectly happily on the side of the hill.

But Martin was sure something wasn’t right, and a few moments more, scanning the horizon for familiar landmarks convinced him that he was in big trouble.

Ianto and Alun had left Wales. They were following the Satnav direction through the Gloucestershire countryside. Alun had taken over the driving seat at the border and Ianto was reading up about their destination on his iPad.

“Belas Knap, Winchcombe is a superb and stunning example of a 'Severn-Cotswold' chambered long barrow dating from the mid-Neolithic period of pre-history – possibly around 4,250 BC.”

Alun let his husband’s voice drift over him without paying attention to the actual words for a while. There was something about the length and width of the barrow and a false portal behind which five children’s bodies had been found in the late nineteenth century.

“Children?” he queried.

“There was a TV programme about that sort of thing a couple of weeks ago,” Ianto explained. “The Belas Knap burials and some others in Northumberland were compared, as well as one in Ireland and another in Denmark. The theory is that they were sacrificed to one of the gods in order to ensure a good harvest.”

“Nice!” Alun shuddered and dropped out of the discussion again as Ianto read aloud about the forty bodies of adults and children found in two historical excavations in 1863-65 and 1928-30 and the partial restoration of the barrow entrance in the 1930s.

“Don’t tourists mess with it?” he asked.

“It’s a bit out of the way,” Ianto replied. “Tourists generally don’t want a long slog uphill for a few drystone walls covered in moss and some dark, pokey holes.”

“Just remember the bit about pokey holes when we get there,” Alun said. “And don’t get all National Geographic with the people from Swansea University.”

“National Geographic?” Ianto laughed. “Besides, I think we’re going to be more Fortean Times. Professor Lloyd said there was something we need to look at – something in our line of work.”

“Not more alien skulls?”

“I don’t know. She sounded a bit upset.”

“She’s a forensic archaeologist. She deals with people who’ve been dead and buried since 4,250 BC. What’s there to be upset about?”

“We’ll know once we slog up the hill. They have a full scale dig going on up there. They’ve got all the latest tech to show them hidden stuff that the historical investigations missed.”

Ianto went on at length about the technology used to identify voids beneath the ground that might be burial chambers or denser areas that would indicate walls. Alun concentrated on driving along the narrow country lane with signs every so often indicating the steepness of the incline. It wasn’t exactly the Black Mountains, but he was glad the Audi had good brakes. A less impressive car could easily start rolling back downhill.

He parked the car presently in a lay-by already tightly occupied by two mini-buses and a land-rover bearing the logo of Swansea University and a Range-Rover with a livestock trailer attached. He and Ianto changed into wellingtons from their well-polished leather shoes and put their overcoats on. It was still only early spring and the wind could be charitably described as ‘brisk’. They climbed the wooden stile beside an English Heritage sign pointing the way to Belas Knap and set off uphill on a rough path between a grassy meadow and a small coppice of deciduous trees that were just starting to come into leaf after the winter.

The camp where the students and professors were staying was at a decidedly odd angle. There was very little flat ground here. Ianto and Alun wondered what it must be like sleeping that way and remembered a pub with bed and breakfast accommodation a few miles back on the main Winchcombe road. If they had to stay overnight it would be where there was the possibility of a hot supper and a properly horizontal place to sleep.

Beyond the camp was a wide ring of standing stones. A group of the students were measuring them, recording the height and width of the stones and the gap between them. Alun and Ianto walked past them to the exploratory trenches near the long Barrow and the line of canvas-sided gazebos providing cover for the archaeologists to work in.

Professor Rhiannon Lloyd came to meet the two men from Torchwood. She knew them both well enough by now. They had worked closely together on the mystery of the alien skulls at Parc le Breos and several other peculiar incidents, since.

“Good to see you, Professor,” Ianto said to her as they shook hands.

“Please, call me Rhiannon,” she answered. “We’re fairly informal out on field projects.”

“What is it you wanted to show us?” Alun asked, wondering if the Professor realised that he and Ianto were together personally as well as professionally and deciding to cut through the small talk just in case. “Have you found something of interest?”

“More like it found us,” Rhiannon answered. “Come inside. I’ve got some pictures to show you.”

She brought them into one of the very portable gazebos. The fresh breeze near the top of the hill was having a good try at raising it up from the weighted base. The board on which she had pinned a series of photos of the surrounding area wobbled alarmingly.

Even so, it was perfectly obvious that there was something odd about the pictures Rhiannon was showing them. They were not pictures of the Barrow, but of the view from the Barrow. Some of them were prints of very old sepia photographs - Victorian men with their trousers tucked into their laced up boots posing heroically. Others were more up to date. One of them was an overhead view with the Google Earth symbol in the corner. Ianto looked at it closely and turned to the Professor with a puzzled expression.

“The standing stones… where are they?”

“Good question,” Rhiannon answered. “They’re not in any of these photos, including these which were taken by one of my colleagues two weeks ago when he came out here to do an initial evaluation of the site. If you look in any of a dozen books that reference Belas Knap, or any website about the Neolithic period in British history, none of them mention standing stones near the Barrow.”

She paused for breath.

“Until this morning, when we woke up in our tents, they weren’t there.”

“Seriously?” Alun looked at her with a measure of surprise. Despite seeing a great many things in his career with Torchwood, an ancient ring of standing stones that only appeared within the past twenty-four hours was a new one.

“Seriously.”

“They’re real?” Ianto asked. “Not polystyrene…” Visions of the stage props from Spinal Tap swam through his mind, but he shook his head and laughed at himself. “No, they’d be blown all the way back to Cardiff by now. Something stronger, but still portable, for a film set.”

“They’re real. My students have been acting like kids playing British Bulldog, running up and touching them. Plus we did some geo-phys on the area. We measured the density of the stones and the depth. They’re buried deep, at least three-quarters of the visible height goes down into the ground. It’s as if they’ve always been there. But… that’s impossible.”

“At Torchwood we have a sort of swear box for whenever somebody says that and it turns out it IS possible,” Ianto said. “Alun used to have to put a quid in it nearly every day until he got to know better. There will be an explanation. It just won’t be one you can tell to anyone whose respect you want to keep.”

“All right,” Rhiannon conceded. “So where do we go from here? What do we do about these stones? Do we do anything? Or….”

“I think I’d like to take a closer look at them,” Alun suggested. “I can take readings… check for unusual energy levels.” He brandished a pocket sized gadget that made a Geiger counter look pedestrian. It had been designed by Toshiko Sato in the Glasgow office and sent down to Cardiff for a thorough testing. It could detect fifty different types of energy particles, some of them not even known about by the best twenty-first century Human physicists.

Alun really wanted to make it fifty-one. He was sure these stones would provide him with his own personal target.

“I’ll come with you,” Rhiannon offered.

“I’ll take a look around your dig,” Ianto said. “It all looks interesting.”

That wasn’t exactly his reason. The mysterious stones clearly were the centre of something right within Torchwood’s remit, but it was always possible that the cause of the phenomena was on the periphery. Perhaps it was the dig - disturbing the ancient site - that created the anomaly.

So he walked along the exploratory trench looking at the work being done to uncover shards of pottery that might be historically significant in some way.

At least that was what he thought they were uncovering until he looked closer. Then he understood the reason why the gazebos had been erected over the trenches. They obviously didn’t want any country rambler stumbling across this.

They had uncovered a series of Neolithic graves all in a remarkably straight row along the western flank of the Barrow. He counted fifteen whole skeletons of different sizes – men, women and children all buried together - before he actually lost count. There might have been at least twice as many.

“How did they die?” he asked. “Were they sacrificed?”

“No,” answered one of the graduate students working on uncovering a pitifully small skeleton. “So far as we can tell, the cause of death was not traumatic. These bodies are as intact as we can expect from some four thousand years in the ground. We suspect some sort of disease that swept through their community.”

“Four thousand?” Ianto did the maths. “That’s about the same time as the Barrow? So why weren’t they buried within it?”

“Because they weren’t important enough,” the graduate said with a shrug. “There’s nothing unusual there. If you’re looking for a mystery, Molly Edwards over there has the really big one.”

Ianto didn’t know what he meant, but he followed the direction indicated by the hand wielding a mud-covered trowel. He found Molly Edwards, her hair in a practical pony tail, wearing cargo pants and a university sweatshirt. She was kneeling on a hessian sack next to one of three skeletons lain side by side. She had her hand within the exposed ribcage picking out what looked like small pebbles. Ianto crouched and took one of them from a small pile and examined it closely.

“It looks like an amber bead,” he said just in passing. “I suppose the thread holding them together must have rotted away, but a thing like this is practically indestructible.” He rubbed some of the soil from it. The bead was remarkably well preserved. The hole through it was full of dirt, but it looked amazingly precise for something that pre-dated power tools.

“It’s funny,” Molly commented, almost absently. “Rhiannon is wearing a necklace just like that today. She’s into that sort of thing – traditional jewellery.”

“I didn’t know amber was used in this country as early as the Neolithic era,” Ianto commented. Then he glanced down at the bodies Molly was working on. “Your colleague said there was something unusual about these skeletons. Surely amber beads isn’t all there is to the mystery.”

“They’re all taller than any adult male or female we’ve seen so far. They’re two men and a woman, by the way. Their limbs are straighter and longer than we would expect, their teeth in better condition…..”

Molly stopped talking. Ianto had given a gasp so filled with grief and pain that it silenced her. He jumped directly into the trench and reached out to touch the skeletal hand of one of the males. She watched him lift the hand and hold it next to his own.

She gasped in astonishment. The Neolithic skeleton was wearing a ring that, if it was cleaned and polished, would probably be identical to the one Ianto was wearing on his third finger.

“No!” he cried out. “Oh God, no! It can’t be. It can’t.”

“Hey!” Molly exclaimed as he pulled the dirt encrusted ring from the skeletal hand before scrambling out of the trench and running out of the tent.

He ran part way up the slope, away from the archaeological camp, away from the mysterious standing stones. He kept running until he found a place where he could get a mobile phone signal and collapsed onto the long meadow grass as he placed the call to Torchwood Cardiff. He was breathless not only with running but with crying at the same time.

“Jack!” he sobbed when a familiar voice answered his call. “Jack, Alun is dead.”

Jack got there in an hour. He had ignored all speed limits and made sure every traffic light was green ahead of the Torchwood SUV. When he hurried up the hill, pacing himself so that he didn’t get out of breath or red in the face, and his hair was only excitingly out of place, he found Ianto sitting on the grass, still crying, his eyes red rimmed and his cheeks raw from the tears that streaked them.

“Ianto, I’m sorry,” he said as he knelt beside him and embraced him like a child, holding him until the sobs gave way to something more coherent. He listened as Ianto explained what had happened and didn’t waste any effort disbelieving his story. He looked at the standing stones that shouldn’t have been there, the stones Alun and Rhiannon were going to investigate. They looked no more sinister than any such ancient monument looked, but he already had a theory based on Ianto’s account of what had occurred.

“They’re called The Lonely Assassins,” he explained. “Usually… they look like statues, the sort you get in graveyards or public gardens, but that lot must be really, really ancient.”

Ianto raised his head from Jack’s shoulder and glanced at the stones, then he looked away again.

“They’re alien?”

“I’m not sure. I think they might have been once, but they’ve been on Earth, lying low, springing their traps every so often, for so long they might as well be indigenous. They snatch people out of time. They leave them in the past and feed on the life energy left behind. They got three victims so far. Three Humans, anyway. The farmer who owns this property has been missing since early this morning. I checked local police reports. It’s possible his sheep were taken, too. Apparently they ought to be grazing on the hill. Alun and Rhiannon were next.”

“But there were students all over the stones. They were measuring them when we got here.”

“I… don’t know,” Jack admitted. “Maybe a farmer and his sheep took a while to digest.”

Ianto shuddered. That was a very bad analogy.

“Come on,” he said gently. “You’ll get piles sitting on this damp grass - or lumbago or something. The students have a mess tent. Come and have a cup of tea…. or coffee.”

“They’ve only got instant,” Ianto answered. But he let Jack lift him up and he walked beside him as far as the tent where most of the students were now congregated. Strange rumours had gone around the camp and the arrival of Ianto amongst them, his grief all too visible on his face, only confirmed them.

One of the students came to him with a hot cup of tea and a bacon sandwich. Ianto accepted both gratefully, but neither the drink nor the food gave him comfort. Nothing could.

“I’m going to take a look around,” Jack told him after a while. There really was nothing more to be said and no comfort he could give. “Hang in there, Ianto.”

He hugged his former lover tenderly. Even that didn’t help. Ianto had long ago left his arms for another man – the one he had lost in an instant of cruel fate. There was nothing physical he could do for him.

The only thing he could do is refuse to accept the situation as it stood.

He walked up to the trenches where the bodies had been found. Molly was still there, trying to do something – anything – about the three modern humans who had been thrown back in time.

“They… ought to have proper Christian burials,” she said turning her head away from the remains but unable to properly look Jack in the eye, either. Her gaze was somewhere over his shoulder. “It feels… I’ve worked on sites like this before. We treat the skeletons we find with respect… not like bits of pottery. We CARE. But… this is different. Knowing… knowing….”

“Yeah.” Jack answered. He felt incapable of anything else. It was hard to believe that the grey bones still covered in eons of mud really were Alun Llewelyn only a few hours ago. A scan with one of the lesser used functions of his vortex manipulator confirmed the truth. It identified his DNA somewhere deep within the dried up remnants of a once living body.

The Vortex Manipulator. He stared at the futuristic gadget on his wrist for several seconds, then he turned and dashed out of the tent. Unlike Ianto he didn’t have to go anywhere to find a mobile signal. A special friend had once fixed his phone so that it worked anywhere and could literally CALL anywhere.

He needed that friend now. He found the number – one with more digits in it than any ordinary telephone number – three of them not even found between 0 and 9. The phone rang for at least half a minute before it was answered. Perhaps he was busy. Perhaps he was deciding whether to answer the call.

Anyway, it was answered. Jack didn’t recognise the voice, but he knew it was him, one way or another.

“I need you,” he said. “I need to be able to travel in time. Either come and get me, or tell me the code to activate my Vortex Manipulator so I can go myself.”

“Why?” The Doctor asked.

Jack told him.

“You’re right. It must be the Lonely Assassins. That’s a new trick for them. But it fits.”

“That’s why I have to get Alun and the other people back.”

“I’m sorry, Jack, but you can’t. The whole site will be quantum locked by them. If you try anything like that it could unravel the whole of reality.”

“Three people will die four thousand years before they were born if I don’t.”

“I’m sorry.”

“Don’t give me sorry. Give me answers,” Jack argued. “Give me what I need to save them.”

“Jack, you CAN’T time travel, not in a TARDIS or with a Vortex Manipulator. Don’t think I don’t understand. I have two friends I can never meet again because the whole of Manhattan is in such a fragile state I daren’t even park the TARDIS in orbit over the area.”

“At least they’re alive. You haven’t looked at their bones lying in the ground.”

“Jack….”

“Tell me what to do!” Jack’s voice raised in anger at the man he considered his dearest friend. He felt betrayed by his refusal to help – after all they had been through together. “Tell me, please.”

“Jack, you CAN’T use time travel,” The Doctor again emphasised. “But listen to me. Listen, carefully. Being quantum locked means that anything done to the Assassins in the present doesn’t just resonate into the future, but into the past, too… the far past and the recent past.”

“What?” It sounded like nonsense. Resonances into the past. What did that mean?”

Then Jack realised what he had been told.

“You mean if I….”

“I once told another friend that you can’t kill stone. But….”

“Doctor… I get it. I do. Thank you.”

He almost dropped the phone in his excitement. He stood for a moment looking at the stones that had caused so much trouble, calming himself both mentally and physically. Then he placed another call, and two more after that once he found out the information he needed.

He went back to Ianto and sat beside him. He held his hand and leaned forward to kiss him on the cheek.

“Trust me,” he whispered. “I’m not finished yet. Hold on in there, Ianto.”

Ianto turned and looked at him with hope in his expressive eyes.

“You mean….”

“I’m not sure. I can’t make any promises. But I’m going to try something. Just hold on for a couple of hours.”

“Jack… thank you,” Ianto replied. “For trying.”

“Anything for you.” He embraced him again, not as a lover, but as a friend who had once been a lover, and who would do anything to stop his heart from breaking as it was right now.

The hours passed slowly. The students and graduates were all quietly taking in the fact that the leader of their expedition was dead. Ianto and Jack grieved for her, too, but mostly they kept a private vigil, waiting for the chance to try to make it all right.

The means to put Jack’s plan into action arrived with a rumble that silenced the crowd in the mess tent. The cups laid out beside the tea urn rattled as the noise got louder. Many of the students ran outside to see what new terror was arriving in their midst.

They were variously startled, excited and appalled at the deep swathe dug into the meadow as a mechanical digger and a Caterpillar with both demolition ball attachment made its way up the hill followed by a JCB roller and a tractor pulling a crop-spraying tank that, as it drew closer, proved to have a hazard sticker on it indicating that the contents were acidic.

“What is all this, Jack?” Ianto asked as he, too, came to see what was happening. “How can this get Alun back alive?”

Jack didn’t explain in words, but as the mechanical leviathans came to a stop he ran up to the digger. He climbed into the cab in one single bound. The driver gave him the keys and his hard hat and climbed out, pulling his high-vis jacket around him against the distinct nip in the air as he joined the crowd of students watching events unfold.

Jack moved the digger closer to the standing stones and brought the huge iron scoop down, digging under each of the stones until their deep roots were exposed just like teeth being extracted. When that was done he parked the digger and jumped up into the Caterpillar instead. He brought that into position and applied the stabilisers before swinging the wrecking ball. Each time it struck one of the stones it cracked it into several pieces. He kept going for nearly an hour until the huge stones were toppled and broken.

Then he waved to the JCB driver. He did as he had been instructed - driving the roller over the broken stones, back and forward until they were crushed into pieces suitable for laying down as aggregate before tarmac was applied to a road surface.

Then Jack took over again. He drove the tractor in close and sprayed the area where the stones had stood with the hydrofluoric acid from the tank. The stone fragments fizzed as the acid attacked them and they began to dissolve before the eyes of the thoroughly perplexed crowd.

“THAT is how you kill a stone,” Jack announced triumphantly as he made the acid gun safe and turned from his work. He noted that there were suddenly a lot of sheep in the field. A man dressed for that kind of labour was trying to herd them away from where toxic fumes were still rising as the acid ate away at the stones.

“You’d best get a fence put up around that area,” he told Martin Garvan, landowner, who had been missing since before dawn. “It will be a while before the sheep will be safe wandering around there.”

“I’ll… do that,” he answered. “How did… I was….”

“In that tent over there you can get a cup of tea,” Jack told him. “I’ll be coming to talk to you about what happened in a bit.”

He turned from the farmer to where Ianto was hugging Alun as if hugs were going out of fashion. Professor Rhiannon Lloyd didn’t have anyone to hug, but Molly and some others of her colleagues were reaching out to grasp her hand, asking a dozen questions at once.

“I think we ALL need tea,” Jack said. “Professor, I’m here to debrief you, and believe me, right now, I am too knackered to make any innuendo out of that.”

Time was, the tea urn would have been laced with Retcon and everybody would wake up tomorrow oblivious of what had happened. But Jack didn’t use his little white pills quite so often lately – as long as the situation could be contained some other way. Only one very excitable student who was having a small mental breakdown in the corner of the mess tent needed treating that way. One of the graduates agreed to drive him to the nearest hospital and book him in with a case of severe agoraphobia. Everyone else was prepared to live with their unique experience of the Lonely Assassins without telling their tale to any conspiracy theory website.

Martin Garvan was feeling better for a cup of tea. He talked about what he had seen. Alun and Rhiannon confirmed it.

“There was a settlement further down the hill,” he said. “People wearing furs and skins and living in mud and grass huts. I think they might have got hold of one of my ewes for their supper. There’s one missing.”

“We didn’t go near them,” Alun added, meaning the people of the mid-neolithic settlement, not the sheep. “They didn’t look very healthy. Besides, the sight of us would scare the living daylights out of them. I suppose… if we hadn’t been rescued, we might have had to make friends with them. I don’t know what we’d have done for food or shelter, otherwise.”

“I wish I could have got closer to them,” Rhiannon said regretfully. “All the time I’ve studied the remains of their lives, digging in the dirt for clues, trying to guess what I couldn’t know for certain. The opportunity….”

“No,” Jack told her quietly. “All that would have happened is that you would have died along with them.” He looked at his Vortex Manipulator. It was in yet another mode. “Rhiannon, you’re incubating a strain of influenza. In a couple of days you’ll be ill. So will just about everyone you’ve been in contact with. You’ll get over it. Everyone will. But those people back there in the past would have had no immunity to it. They would have died.”

“Would have?”

“Ask your colleagues. When you all returned from the past the three skeletons Molly was working on vanished, and so did all the others. You’ve got nothing but empty trenches. There was no epidemic to wipe them all out leading to the mass burial in front of the Barrow.”

“You mean…..”

“Bringing us back saved their lives as well as ours,” Alun concluded.

“I am glad,” Rhiannon admitted. “Except….” She paused. What she was about to say sounded more than a little heartless in the circumstances. “Without the skeletal remains we’ve wasted two weeks work. I don’t know what I’ll tell the university.”

“You know exactly where to start digging new trenches to uncover the remains of the settlement,” Alun reminded her. “That’ll be a big project for you all.”

“Another good reason not to administer the Retcon,” Jack thought as he sipped the instant coffee and tried not to mind how bad it tasted. Later, when he felt a bit calmer, he needed to call that number again. He needed to thank The Doctor for telling him how to fix this problem without actually telling him how to fix it.