I’m an archaeologist. Or rather, I’m an archaeology graduate; I completed my degree last year, and I’ve been trying to get onto a postgraduate course since then. It’s a competitive field, with few positions open; I narrowly missed my chance last summer, and I’ve been working in a bank while I apply for more positions.

I studied at an English university, specialising in the Saxon settlement of Britain in the 6th century. Last month one of my professors, who I’ll call Sharon, emailed me; somebody had found a possible new settlement. I won’t say exactly where, but it’s further west than any previously known Saxon village. She had been excavating for some time, and needed help with the work. I was wary of leaving the bank at such short notice, but when she hinted that additional funding for the dig might lead to a postgrad position opening up, I stopped caring about my reference from the bank.

So the next morning I was on a train with little more than warm clothes, a sleeping bag and a laptop. By lunchtime I arrived at the station, and Sharon picked me up and we headed out to the site.

England is very heavily developed, and you’re never more than a few kilometres from at least a small village. So the fact that we drove offroad in the Jeep for nearly half an hour was quite remarkable. Apparently some Scouts had been on a hiking trip and found a mostly buried wall. This sort of thing must happen all the time, but this time they had mentioned it to their scoutmaster, who was a historian and took an interest, eventually leading to the university getting involved. By the time I got there the excavation had been going for a while; the outlines of several buildings were visible, and I estimated the settlement would have housed around 30 people. Sharon helped me set up my tent, and then gave me a tour of the site.

There were five of us at the site in total. I had no specific job, but suspected I was mainly going to be doing the physical work. Sharon had twenty years’ experience on me, and as the site lead would be responsible for writing reports; the university was going through an efficiency drive and she had to submit daily reports to justify the expense of the dig. “Mark” and “Penny” were undergrads, and “Justin” was an 18-year-old taking a gap year, so as the second most senior person there, I was also in charge of documentation. We were a very young group, and only I and Sharon were taking any remuneration for the work. If we proved the site worthy of additional funding before Justin, Penny and Mark had to go home, no doubt more experienced archaeologists would take their place, so I was very conscious that I had a limited time to prove myself.

This was October, and by the time I had set myself up the light was fading fast. But keen to get to grips with the site, I spent the last hour of daylight studying the layout, sketching and making measurements. Given my knowledge of similar settlements I made some predictions regarding the extent of the site, and where we might find further buildings. Judging from the rest of the architecture, I figured the settlement might be post-Christian, and estimated possible locations for a church.

I spent the next two days looking for the church. Given the lack of funding we had very limited equipment, but I’d been right about the location. On the third day I uncovered part of a stone wall, a strong indicator of a church, and got Justin and Penny to help me uncover the shape.

It was two days later that I found it. Justin was off helping Sharon, and Mark was taking lunch, so I was working on my own, uncovering the floor of the church. As I slowly scraped the soil with my trowel, I saw a hint of orange. I pulled out my brush and carefully cleaned the area, to find what looked like an orange thread, buried in the ground at both ends.

This concerned me, although at the time, not for the right reasons. Orange thread was far from anything I associated with the Saxons. I called Penny over, as I knew she had an interest in Saxon textiles. She agreed that this was unlike anything she’d seen before; most likely, the site had been contaminated recently. But we couldn’t be sure, so Penny and I brushed the area to reveal more.

After an hour we had uncovered a network of threads about half a metre across. They ran through the ground in an organic pattern, like fungal mycelia. One thread had been uncovered sufficiently for Penny to put her finger underneath and lift it up; before I could stop her, the thread snapped. It quickly turned to dust, causing my nose to itch and Penny to sneeze. I reprimanded her for her carelessness, and we then agreed to cover it up. It was early evening, and we didn’t want moisture to affect the area. Our limited budget hadn’t even given us an excavation shelter, so we just put a sheet of polythene over the area and weighed it down with stones.

Sharon knew no more than we did about the likely provenance of the orange threads. She took some photos and told us to leave it undisturbed until some of her colleagues had a chance to review it. And with the sun setting and Sharon typing up her daily report, the rest of us had a couple of beers and settled in to sleep.

I awoke around 6 the next morning to the sound of car engines. Pulling on my shoes and coat, I crawled out of the tent. Sharon and Mark were already up, watching four black SUVs pull up and park next to the camp. A man in a crisp black suit stepped out of the lead car, and demanded curtly to speak to the project lead. He and Sharon walked off and began talking. I couldn’t make out much, but I did hear Sharon raise her voice in argument a few times. The others were out of their tents now, and we spent about fifteen minutes in wild conjecture until Sharon and the suit walked back. Sharon told us that the project was over, and we needed to pack our tents and leave immediately.

Of course we argued. This dig could make my career, and besides, Penny and I were very keen to learn more about the orange threads. There was no way these interlopers had the slightest clue about archaeology, and would no doubt ruin the site if left alone with it. But in half an hour we’d packed our things and were in our cars. During the whole time nobody else stepped foot out of the black SUVs. We left, and Sharon gave me a lift back home.

I was in a dark mood that evening. I hadn’t pleased my line manager at the bank when I’d quit without notice, so doubted they’d take me back; and it looked like my chance for a PhD was gone. But in the morning as I settled down to search for jobs, I got a phone call. Sharon wanted the five of us to continue working. We may have been kicked off the dig site, but they couldn’t stop us reviewing what we’d found so far. So on Monday I met Sharon, Mark and Penny in a cafeteria at the university. Justin had apparently made other plans.

Between sketches, measurements, notes and photographs, we had actually gathered quite a lot of data, and it would likely take a couple of weeks to review it all. Sharon worked with Penny on mapping out the site in detail, and I worked with Mark on a literature review of comparable sites. But as the day wore on I started to feel unaccountably wary of Mark. I’d got on with him very well at the site, but now he felt … off, somehow. The more I looked at him, the more I felt uncomfortable, as though being in the same room was dangerous, though I couldn’t quite put my finger on it.

The next day didn’t ease my feelings. Something just seemed wrong; not the “creepy guy” vibe I’ve got off some men, but more a sense that he was planning something nefarious. I confided in Penny over a coffee at lunch, and she confessed that she had got a similar feeling from Sharon.

By Wednesday I was feeling a little under the weather, but able to go in. When the four of us met, Mark asked if I was okay. I wouldn’t normally remark on this, but the way Mark said it … it felt very accusatory. Sharon said I should work from home. I glanced at Penny, who just shrugged. Were Mark and Sharon planning something? To be honest, Mark and Sharon looked worse than I felt; pale, perhaps, and their posture seemed vaguely threatening. I didn’t want to leave them unsupervised, and insisted that I was fine to continue. Before settling down to work I managed to catch Penny alone at the coffee machine.

“Do I look okay to you?” I opened.

“Yeah, a bit tired maybe. I don’t … I thought they were out of order back there.”

“I don’t trust them. Can you keep an eye on Sharon?”

“Sure, actually I was going to say the same to you. See if Mark’s acting weird, we can catch up at lunch.”

I found Mark in the spare office we were using, with the papers already out. As we got to work I studied Mark, noting his expression and posture. Again it was subtle, but there was definitely something not right. I caught his dark brown eyes, and for an instant they seemed to flash orange. Then suddenly he exploded.

“WHAT?!”

“What do you mean?” I replied calmly.

“You’ve been staring at me all morning. Have you got something to say?”

“No, I …” What could I say? “I just …”

“Look, if you want to ask me out, just come out and say it.”

I was astonished. What did he think was going on?

“I uh …” I had no idea what to do. “Umm, we should just …”

I looked down at my papers. I started to collate the citations, but had barely listed them all when Mark said he was going to lunch. It couldn’t have been ten o’clock yet, but when I looked at my phone, it was half past twelve. I glanced at Mark’s work, and he’d done at least three hours worth of work. I’d felt a bit unwell, sure, but how had I lost two hours?

Mark got up and left. I could have carried on, but Penny had agreed to meet for lunch, so I headed down to the cafeteria, to find her sat down by herself. I grabbed a sandwich and water, and joined her.

“So,” Penny started in a low conspiratorial voice, “anything to report?”

I recounted the outburst, the strange conversation, the odd body language. I almost didn’t mention the flash of orange I’d seen, or thought I’d seen, in Mark’s eyes; but when I did, Penny gasped.

“I saw that too!”

“In Mark?”

“No, in Sharon.”

“Wow, okay. That’s weird. Any ideas?”

“Well I wasn’t going to say it. I thought it was my imagination, but –” Penny leaned in closely and lowered her voice even more. “You remember the threads we found at the dig?”

“Of course, they …” Suddenly I realised what she meant. “They were the same orange, weren’t they?”

“What does it mean?”

“I don’t know,” I replied, “but I’ve got an idea. Let’s meet at five.”

“No, I don’t feel good staying here with Sharon. Tell her you’ve decided to go home after all, and I’ll make up some excuse. Why don’t we meet in my halls of residence? It’s only ten minutes from here.”

So Penny and I left the department early. Penny had a single room in her halls of residence, even smaller than my old one, and we cleared as much space as we could on her tiny desk. She offered me a coffee, but I didn’t feel like one, and neither did she. The coffee that morning had tasted very bitter, so with a glass of water each and some notebooks, we started writing everything we knew.

“What’s cordyceps?”

Penny had glanced over at my notes before I was ready to compare.

I explained what I knew. “It’s a fungus. It infects ants, and controls their brain. It takes them somewhere more suitable for the fungus to grow, and slowly eats them, converting their body into more of itself.”

Penny looked disgusted for a moment, and then realised what I was getting at. The orange threads from the dig site, that were most likely mycelia – had they infected Sharon and Mark?

Penny opened her laptop and Googled cordyceps. I’d got a few things wrong, but the basic principle was correct. “Do you think that’s what it was?”

“Well no, not cordyceps, that only infects ants. But something like it. Something that can control humans would have to be more complex, I suppose.”

“Well, we both saw the orange in their eyes. The eyes are part of your brain, sort of. I guess it would explain their weird behaviour, right?”

We talked about this for a long time, bouncing theories off each other. Something that could infect the complex brain of a human – well, it would have to be more sophisticated. The government agents that had closed down our dig site had arrived so quickly. They must have already known about the fungus, but not about that site. So there must be other sites. Could they be linked together, operating as a neural network across the country – even across the planet – an intelligent fungus, infecting hosts to achieve … whatever their aims might be?

We realised that the agents had arrived too late. I don’t know why they didn’t quarantine us, but we had no way of contacting them. We could have asked Sharon, but if she was far enough gone, she wouldn’t help us. We had to do something ourselves.

I don’t remember whether it was myself or Penny who first said it, but we reluctantly agreed that it was the only option. We had to stop the infection from spreading. We sat up late into the night, planning our next steps, and I slept on Penny’s floor. I’d gone home sick that day, so I would pretend to be ill and collect the equipment we needed, except for the car – Penny texted her brother asking to borrow his, saying she needed it for a university project.

The next morning, Penny went in to the department. I tried to persuade her not to, but she insisted that somebody needed to keep an eye on the disease’s progression. She was right, of course. I spent the day gathering supplies. It would have been easier to wait for the car, but we had to move fast. I met Penny that afternoon, somewhat relieved that she was okay, and her brother dropped the car off. He wanted to stay and enjoy the university life for a night, but we had work to do, so Penny made some half-hearted excuse and he took the last train home.

We checked our equipment, went over the plan again, and for a second night I slept on Penny’s floor.

The next day we went to the university. I walked while Penny drove, so that we didn’t arrive together and arouse suspicion. That morning was one of the most difficult few hours of my life, pretending to Mark that everything was normal. He looked different, twisted somehow, though nobody but Penny and I seemed to notice. Sharon was the same.

We took Sharon and Mark out for lunch. We told them that we were so happy to be part of this project that we wanted to repay them. Our treat, we said. Sharon protested, saying that it should be her to pay for all of us, but eventually they agreed. I normally like Mexican food, but it tasted strangely sour, as though the ingredients had gone off somehow. But we weren’t there for pleasure. Our plan was risky, but it worked; I won’t explain what the drug was, or how I obtained it, but I managed to slip it into Sharon’s and Mark’s food without them noticing.

We kept them there “celebrating” for an hour or so, long enough for the drug to take effect. By this time, Sharon and Mark were feeling ill, and Penny offered to drive them back to the department. She had left her car in the restaurant’s car park, and we helped them into the back seat; I got into the passenger seat, and Penny started to drive.

Of course we weren’t going back to the university. We drove about half an hour out of town, to an area of scrubland, far from any houses, and drove out of sight of the main road. Penny feigned concern, and suggested to Sharon and Mark that they might want to get some fresh air. Eventually they agreed, and we helped them out of the car. We then went back to the car, collecting the two hammers I’d bought the previous day. Drugged as they were, we still needed to take them by surprise. I struck Mark three times in the head, and Penny hit Sharon twice. That was enough to stop them moving. I don’t know for sure if they were dead at this point, but we were sure there was no coming back from that.

Penny covered the back seats with plastic sheeting while I did my best to make sure their injuries weren’t obvious; then we put them back in the car. Penny drove for four hours while I navigated, and as night started to fall, we arrived back at that cursed dig site.

We had expected this to be the most difficult part of our plan, but the agents were nowhere to be seen. I have no idea why not – for all their apparent aggressiveness, did they not realise precisely what they were dealing with? The alternative – that they had themselves become infected – was too terrible to contemplate. Still, it made our task far easier. We parked as close as we could, and dragged the bodies the remaining fifty metres to lay them in the ruined church. If they were infected, then so was the ground, and we could at least contain the infection. Also, it was likely that nobody would encounter the bodies for months or perhaps years to come. And so we left Sharon and Mark to rot in the infected soil, and drove back. It was four in the morning when we arrived, and we went back to Penny’s room.

Our task was done. (Or so we thought.) We celebrated with a bottle of wine, but the wine had gone sour, so we abandoned it and went with water instead.

At that point it was Saturday morning. Neither of us were feeling great, and we spent most of the weekend in Penny’s small bed watching Netflix. We decided to go in on Monday morning, so as not to arouse suspicion, and continue working on the archaeological write-up.

Over the course of that day, we realised that we’d acted too late. Other people in the department had strange expressions, or orange-tinted veins in their eyes. We went out for lunch, each having a salad and water, and our server looked infected as well. I don’t understand why Penny and I are the only ones who can see it.

Our task is clear now, though. We’ve done it before, and we can do it again. We must do it again. We must cleanse the world of this fungus, killing the infected and taking their bodies to that ancient Saxon church, before it spreads beyond our control. If it hasn’t already.