The Tachyon Solution

A Sci-Fi Short Story written by Greg Tulonen

The Tachyon Solution

by Greg Tulonen 

Greg Tulonen writes novels and screenplays, short stories and comic books, web series and audio dramas, and an occasional play. His projects include the award-winning supernatural web series “Ragged Isle,” the acclaimed vampire graphic novel “Night is Falling,” and the science fiction novel “Dr. Xivray and the Presidential Peril,” which was called “the most important book you will ever read” by some drunk guy in a bar. You can find links to his works on his website,

The dead guy would not stop knocking.

The cadence and profitability of my workday is entirely dependent upon people knocking on my door, and there are some days in which nobody knocks, so any knock at all should be, by any possible measure, a positive development. But on this particular day, I was nursing a sour hangover after a night of revelry celebrating my (at last) finalized divorce, which I was attempting to sleep off. The hangover, I mean. Not the divorce. Well, maybe both.

I was stretched out on my far-too-short office sofa, my attempt at sleep in no way aided by the sun shining through the blinds at exactly the correct angle to hit my eyes, not to mention the dead guy’s incessant knocking. I pulled a couch cushion over my head and waited for him to give up, which he didn’t, so I finally roused myself enough to go open the door, and there he was. The dead guy.

Let me tell you: This guy was in no great shape, his skin pasty and green, and thick white spittle collecting around his lips. He was shaking violently, like someone had put six quarters in him and set him on extra spin, and his pants were torn and muddy, as if he had spent the better part of the morning falling down. He wore a black t-shirt with a complicated-looking equation printed on it in white:

Gμν + Λμν = ΚTμν

Which was, as they say, all Greek to me.

The tachyon solution,” he said, kind of gurgling it as he clutched his throat and fell to the floor of my office. He was thrashing around pretty good by that point. I hope he doesn’t throw up, I thought, which was maybe not the nicest thing in the world to be thinking in the moment, but in my defense, I had just had the carpet cleaned.

I’m a private detective, or private eye, as nobody I know has ever called it in real life. Detectives are only ever called private eyes in books and movies, in which potential clients and various bit players are always bursting into their offices in some over-the-top dramatic fashion, by dropping dead, for example, or pulling a gun, or simply being a mysterious, voluptuous dame, but in each case dragging the detective down a treacherous path of murder and mayhem. The workday of a real-life detective isn’t like that at all. Mostly I do background checks for employers who could have done the same thing themselves if they knew how to use the internet, and if a woman does come through my door, she’s neither mysterious nor voluptuous, but rather on the wrong side of middle age and wanting to know if her husband is cheating on her, which he is, let’s face it, because if she’s bothering to seek out a private detective, there have already been enough clues for her to have worked it out for herself. But I digress. The point is, dramatic entrances are not a thing in real-life private detectives’ offices, except on this day, when the dead guy burst in and said, “The tachyon solution,” like it was something that was supposed to mean something, which it didn’t. Not then.

I keep calling him the dead guy, but in point of fact, he wasn’t dead when he was knocking on my office door, and he wasn’t dead when I let him in, and he wasn’t dead when he said, “The tachyon solution,” and he wasn’t dead when he fell down, flailing around on the floor like a carp in a canoe, and he wasn’t dead when he stopped flailing, looked me straight in the eye, and said, “You have to go to my house! Promise me you’ll go to my house!”

Sure thing, champ,” I said. “Whatever you say.”

Promise me!”

I promise,” I said, and right after that, he was dead.

I went through his pockets and came up with a phone and a wallet. The phone was locked, and it briefly occurred to me that I could maybe unlock it by holding it up to the dead guy’s face, but I wanted to do that about as much as I wanted to take tango lessons with my mother down at the senior center, which was something she’d been bugging me to do, but which I had no interest in doing, much like I had no interest in using a corpse’s face to unlock a phone. So, I turned my attention to the wallet. He had seven hundred and thirty-seven dollars in cash (must be nice, I thought), and his driver’s license and credit cards indicated that his name was Braxton Kairos, so I figured his name was probably Braxton Kairos. Listen: I didn’t get my detective’s license out of a box of Cracker Jacks, which is something you might hear a detective say in a movie but is not really something an actual detective would say in real life. But seeing as how there was suddenly a corpse in my office, just like in the movies, I figure: what the hell?

Most perplexingly, the contents of his wallet also included my business card (“Riley Dylan Private Detective / Swift – Reliable – Discreet”). I couldn’t imagine where he might have gotten it, because while I had a whole stack in my own wallet, it had been a long, long time since I had given one out to anybody.

Having some random guy drop dead in your office can really screw up your day’s plans, even if your only plans for the day were sleeping off a hangover until it was time for dinner. Especially if those were your only plans. You have to report the death, of course, and after that there are going to be questions to answer and forms to fill out. The bureaucracy of homicide investigation is byzantine, and I had no desire to navigate it, not to mention my almost pathological aversion to interacting with cops. So, I called Jo.

In movies and books, the detective always has a buddy on the force who can serve up crucial information and get the detective out of all sorts of jams. Jo isn’t that for me. I knew her in college and we’re friends on Facebook, though we don’t see each other socially and I don’t even know her wife’s name. Still, you work with what you have, and Jo is the only person I know personally who’s an actual cop.

Yeah?” she said when she picked up the phone. She sounded suspicious, as if whoever was calling would almost certainly be bearing bad news. Which I was.

Hi, Jo,” I said. “It’s Riley.”

Riley who?” — not the most promising response, I’ll admit.

Riley Dylan.”

Oh,” she said, somehow making it sound like of all the possible Rileys who might have been calling her, I was the most disappointing, by a considerable margin.

How’s it going?” I said, trying to give the conversation some forward momentum.

Fine,” she said, determined to stop any momentum in its tracks.

Listen, Jo, I’ve got a bit of a situation here.”

She didn’t say anything to that, so I kept going. “A man came into my office and died. I think he may have been poisoned.”

What makes you say that? Did you poison him?”

Well, no.”

Okay. Then why don’t you hang up and call 911?”

Listen, Jo, we’re friends, right?”

I’d say we were more like acquaintances.”

Fine. Acquaintances. As your acquaintance, I’m asking for a favor here.”

Which is what?”

Come to my office and get this body tagged or cataloged or whatever you have to do to dead bodies. I’m going back to my apartment to take a nap, after which I’ll be happy to answer any questions you or your colleagues may have.”

You’ve got to be kidding.”

You know, I didn’t have to call you at all. I could have called a lawyer.”

There was a silence on the line, like the silence that must exist in the vast nothingness of space. “Jo?” I ventured, to see if she was still there.


Do we have a deal?”

Who is this guy?”

His ID says his name’s Braxton Kairos.”

You’re joking.”

Seems like a pretty weird joke.”

Braxton Kairos is dead in your office?”

You say that like I know who Braxton Kairos is.”

Riley, Braxton Kairos is one of the five richest people on the planet. How can you not have heard of him?”

I don’t get out much.”

Well, if it’s true, it’s going to bring out half the force to your office. And the other half will be waiting for you out on the street.”

That’s fine,” I said, “after I take a nap.”

No, not after you take a nap. Immediately. As in, right now.”

I’ll leave my office door unlocked,” I said.

Riley, you better-” Jo began, but I hung up before I could hear what she had to advise. I put my phone in airplane mode and beat a hasty retreat, running down the stairs of my office building at a breakneck pace (and hoping like heck that wasn’t an accurate phrase).

The problem, I realized, as I sat behind the wheel of my car (a twelve-year-old Honda Accord badly in need of new brakes), was that I had no place to go. Or rather, I had plenty of places to go, but no place I could think of offhand that cops wouldn’t think of as well, probably before I did. My apartment was out, obviously, and today of all days, my ex would be in no mood to provide me sanctuary in what was formally our house, or to in any way indulge my semi-fugitive status, which I assumed I had obtained the moment I had disconnected my call with Jo. One by one, I thought of friends and acquaintances, and one by one, I thought of the reasons they would decline my request for help, curse me out, or simply hang up on me. “I should work on my people skills,” I said aloud, to nobody in particular, which seems appropriate somehow.

Braxton Kairos’s phone rang, and that’s when I remembered I still had Braxton Kairos’s phone. I didn’t answer it, and it stopped after two rings. The phone made me think of the wallet, so I fished the wallet out of my pocket to give it another look. His driver’s license gave his address as Kairos Compound One, in the next town over. It was as good a direction as any to head in, I supposed, which was pretty dumb, when you think about it, because the cops I was trying so painstakingly to avoid would surely go to Braxton Kairos’s home just as soon as they were done retrieving Braxton Kairos’s body from my office. But I had made a promise to a dying man, and even if that promise was in no way legally binding (nor did I have any idea what it would actually entail), I figured I might as well at least try to make good on it. Plus, if I wasn’t going to give his wallet and phone to the police (and it seemed I wasn’t), I thought I should probably give it to his family — or, if he didn’t have any family, his butler. (Being as rich as he supposedly was, Braxton Kairos surely had a butler.) I took my phone off airplane mode, fired up Google Maps, and plugged in Braxton Kairos’s address. A reassuring voice reassured me that I was twenty minutes from my destination.

It turned out to be thirty.

The entrance to Kairos Compound One was on Kairos Drive, and I was beginning to suspect that maybe this Braxton Kairos fellow had a bit of an ego. There was a fifteen-foot gate (closed and locked) blocking the entrance, and a twelve-foot-high brick wall on either side of it, stretching out in both directions. There was no little buzzer or intercom by the gate to communicate a request to enter, which seemed nuts. How does this guy get his Amazon packages? I wondered, and then decided that postal workers and other delivery people had probably all been issued little buttons in their vehicles that allowed them to open the gate, and anybody else who desired entry could apparently go hang, as far as Braxton Kairos was concerned. But since Braxton Kairos would no longer be granting anyone permission to enter his property ever again, I (for reasons that now elude me) figured I should jump the gate. So that’s what I did, which was far more difficult and awkward than I just made it seem. On the other side of the gate, I beheld a long, white-gravel driveway, thickly lined with trees on either side, leading in a precisely straight line up to an enormous mansion, as gaudy and garish as a hyperactive child’s birthday cake, built into the side of a gently sloping hill.

My phone rang, and I cursed aloud for having forgotten to put it back in airplane mode. I glanced at the screen and saw that it was Jo, to whom I had no specific inclination to speak, so I hit decline, and seconds later I got a text from her that read: “What’s your game?” A few seconds after that, another text: “Filing a false police report is a crime.”

That last one snagged at me enough to send a single punctuation mark in reply: “?”

Jo replied with a photo of my office, which stood completely empty. Well, not completely empty. My desk was there, and my chairs and my filing cabinet and my far-too-short sofa. But Braxton Kairos’s body was decidedly not there. “Huh,” I said, and put my phone back in airplane mode.

That’s when ten security guards, men and women, all identically clad in black pants and black turtlenecks, stepped casually out from behind trees all around me, all of them holding automatic weapons pointed precisely in my direction. It was very neatly done, this maneuver — simultaneous and coordinated and completely silent. None of them bothered to say anything as ridiculous as “Freeze!” but I froze nonetheless, and seconds later, my wrists were bound behind me with a plastic zip tie and I was being lindy-hopped up the long white driveway toward the house.

At least they didn’t shoot me.

They searched me when we got inside the house, and when they came up with Braxton Kairos’s wallet and phone, it caused no end of consternation to the head guard (at least I assumed he was the head guard, based on his demeanor, and the other guards’ deference to him). He was a big man with a smooth black crewcut and a vein that throbbed at his temple. He took charge of my custody while the other guards presumably went back to their guarding, and the main thing he wanted to know (even more than who I was or what I was doing there) was where I’d gotten Braxton Kairos’s possessions. We were in a large pantry, well stocked with cans and dry goods, and I was sitting on a stool, my wrists still bound behind me, concentrating on not falling off.

I got them off Braxton Kairos’s dead body,” I told him.

Try again.”

I’m serious. I’m sorry to have to tell you this, but your boss is dead.”

I don’t have a boss.”

Are you the owner of this house?”

He said nothing.

Because if you’re not, then you have a boss, and I’m assuming your boss, or your boss’s boss, or your boss’s boss’s boss, is named Braxton Kairos. And Braxton Kairos is dead.”

No, he isn’t.”

Listen: I’m a private detective, and Braxton Kairos died in my office about an hour ago. I think he may have been poisoned.”

He was looking at me the way a teacher might look at a dimwitted child who had just proffered a particularly pathetic excuse to explain some missing homework. “Why are you doing this?” he asked me. “What do you hope to gain?”

There’s nothing to gain. It’s just the truth.”

No, it isn’t! Obviously!”

Why ‘obviously’?”

He rolled his eyes.

Do you want to know what he said before he died?”

What’s the point? There’s no point talking to you. You’re so full of crap, it’s leaking right out of your mouth.”

He said, ‘The tachyon solution.’ Does that mean anything to you?”


There was an audible pop of a loudspeaker activating, and I heard a sonorous voice say, “Bring the detective to me, Courtney. Right now.”

A startled expression flitted across the guard’s face and was gone at once. He stood up and extended a hand to help me to my feet. “Let’s go,” he said.

Your name’s Courtney?”

It was a long, labyrinthine walk to our destination, up staircases and down corridors, with turns and reversals and doorway after doorway, and I hoped I wouldn’t have to find my way back on my own. At last, we arrived at a massive, ornately decorated office that clearly belonged to the house’s head honcho. Although we’d come up several flights, I could see we were still on a ground floor, and I recalled that the house was built into the side of a hill. The vast yard outside this office was clearly at the very top of that hill.

At the far end of the room, behind a desk the size of a battleship, sat the dead guy from my office, Braxton Kairos, wearing the same clothes he’d been wearing a hour or so earlier, though untorn, unmuddied, and altogether more kempt. Also, I couldn’t help but notice, he wasn’t dead.

Thank you, Courtney,” he said. “You may remove those restraints.”

With a disgruntled grunt, Courtney snipped the zip tie binding my wrists.

Kairos said, “The wallet and phone: May I see them?”

Courtney took the long walk over to Kairos’s desk and set down the wallet and phone.

Leave us, please,” said Kairos, with a dismissive wave of his hand.

Mr. Kairos, do you want me to-”

I’m sorry. Did I forget to say ‘now’?”

Courtney did his disgruntled grunt thing again and then left, pointedly not looking in my direction as he passed me. The door closed behind him with a soft snick.

Kairos regarded me from behind his desk. “Have a seat,” he said.

I took the same long walk Courtney just had, Kairos never taking his eyes off me. “Where did you get these things?” he asked, gesturing to the wallet and phone. I was still making my way across the room, and it occurred to me that the architecture of this office was its own sort of power play, as visitors were forced to travel a great distance to get to Kairos, and he could just sit behind his desk the entire time, master of all he surveyed.

I’m not sure anymore,” I said. I had finally reached him. He pointed at a chair, and I sat in it, noting at once that it was positioned quite a bit lower than Kairos’s own chair.

Explain,” said Kairos.

I quickly summarized everything that had transpired that morning. It didn’t make much sense, unless maybe Kairos had a twin brother. “Do you have a twin brother?” I asked him.


Then I don’t have the slightest idea what’s going on.”

Kairos made a steeple with his forefingers and pressed them to his lips. He squinted, as if trying to work out a complicated problem, then lowered his hands to his desk. “When you have eliminated the impossible,” he said, “whatever remains, however improbable, must be the truth.”

Sherlock Holmes, right?”

Indeed. And when Arthur Conan Doyle wrote those words, over a century ago, they may have even been true. But not anymore.”

Why not?”

Because we cannot eliminate the impossible. In fact, the impossible is the only possible explanation.”

I’m not sure I follow.”

Let me show you something.” He produced from his pocket a wallet, placing it on his desk, directly beside the wallet I’d retrieved from the corpse in my office. They appeared to be identical, right down to the scuff marks. “Compare their contents,” he said. “Lay them out on the desk side by side.”

I did as he asked, removing all the cash and cards from the wallet he’d provided, and doing the same with the wallet I’d brought. With the exception of my business card inexplicably included in the second wallet, their contents appeared to be the same. Same driver’s license. Same credit cards. Even the same amount of cash: seven hundred and thirty-seven dollars (must be nice). Kairos plucked a fifty-dollar bill from both stacks of money, and held them up next to each other. “Notice anything unusual?” he said.


Look at the serial numbers.”

I looked at the serial numbers. They were the same. “Counterfeit?” I ventured.


I don’t understand.”

They’re the same bill.”

Yeah, I still don’t understand.”

I know.” Kairos pursed and flattened his lips multiple times. “That business card of yours. Did I have it on me when I came to your office?”

Yeah, it was in your wallet. I don’t know where you got it though.”

You should give me one.”

You can keep that one.”

Kairos shook his head. “Better not. The bootstrap paradox, don’t you know.”

Uh, no, I don’t know.”

Kairos sighed. “If I take the same card you found in my wallet, then where did it come from? You see?”


Just give me one of your cards that’s not this one, okay? Or rather, not this one yet.”

Very confused, I got out my wallet, pulled a business card from the inner compartment, and handed it over to Kairos. He took it silently, almost reverently, and tucked it into his own wallet, along with the cash and cards from the desk, and he put his wallet back in his pocket. The second wallet (and its contents) remained on the desk. Kairos picked up the phone I’d brought with me and held it up to his face, unlocking it. He turned it to face me. “Two hours fast,” he said, and set it back down on the desk.


Kairos stood up very suddenly. “Let’s go for a walk,” he said. He opened a window behind his desk (not a door, like a regular person; a window), and hopped out, as nimble as a cheetah. I followed, somewhat reluctantly, as nimble as a very clumsy cheetah.

I don’t know the exact acreage, but I’d be willing to bet that Braxton Kairos’s backyard was larger than Rhode Island. We walked quite a distance, me struggling to keep up with his long strides, past marble statues and gibbering fountains and broad ponds and exotic gardens and meticulously groomed lawns, Kairos peppering me the entire time with questions about our previous encounter — if indeed it really had been Kairos I had encountered in my office, though I still didn’t see how it could have been.

Tell me again,” he said, “what I said before I died.”

You made me promise to come here. To your house.”

Before that, I mean.”

You said, ‘The tachyon solution.’”

Kairos stopped walking and turned his face up toward the sun. “Does that mean anything to you? ‘The tachyon solution’?”

“No,” I said.

He resumed his rapid pace, and I jogged a little to stay by his side. “No reason why it should,” he said. “It’s a project name that’s so secret, even my top scientists helping me with the tech have never heard it. I keep their research siloed, you see, so nobody knows what anybody else is working on, and only I can see the whole board. So really, there’s nobody who could have said, ‘The tachyon solution’ to you besides me.”

“I still don’t understand.”

“Do you know what tachyons are?”

“I’ve heard of them,” I said, adding: “Not really, no.”

“Tachyons are hypothetical particles that can travel faster than light.”


“Only, they’re not hypothetical. I’ve found them. I’ve isolated them. I’ve contained them in a supersaturated solution. This solution right here.” He pulled from his pocket a small glass vial containing a thick liquid, dull and opaque.

I couldn’t think of anything to say besides “Ah,” so that’s what I said.

We had come to an immaculately manicured garden. Kairos stopped walking and sat on a marble bench bigger than my bed at home. “The implications of this discovery are literally astronomical,” he said. “Faster-than-light communication. Faster-than-light travel. But most applicable to the circumstances in which we currently find ourselves: if you were to consume the contents of this vial, as five lab mice previously have, you would travel two hours into the past.” He said that last bit very mildly, as if he were talking about how nice the day was. “The only problem is,” he continued, unconcerned by (or oblivious to) my disquiet, “shortly after you go back in time, you die. Maybe forty-five minutes. No more. And after you die, your corpse rematerializes in the present, a minute or so after you left. I still haven’t figured out why.”

“Okay,” I said, thinking I might have been better off if I’d stayed and talked to the police, but that reminded me of Jo’s texted photo of my corpseless office, so maybe not. Maybe this was all an elaborate con, but to what end I couldn’t fathom.

Kairos was doing the thing he’d done before, pursing and flattening his lips, over and over again. Then he stopped and said, “Perhaps someone is plotting to kill me, to poison me with my own tachyon solution. Though it’s a mystery to me who would want to do this.”

“Maybe Courtney,” I suggested, for no other reason except I hadn’t liked him very much.

Kairos ignored that and continued his own train of thought. “Maybe that’s why I sought you out in particular,” he said. “To prevent my own murder.” The idea seemed to fill him with awe.

“How would you even know about me?”

“You gave me your card.”

“But I only gave you my card because you asked me to, after I was already here, and I only came here because you made me promise to before you died.” (This was turning out to be the strangest conversation of my life.)

Kairos placed a hand on my shoulder. “If we open our minds to the possibility of time travel,” he said, “we must accept the idea that causality is not necessarily chronologically linear. We must embrace the existence of causal loops.”

I still wasn’t completely buying his story (and I didn’t know what “causal loops” were), but for the sake of the discussion, I indulged him. “Okay,” I said. “Let’s say I prevent your murder, which by the way I have no idea how I’m supposed to do that, but let’s say I do. Then by your own logic you wouldn’t go back in time, you wouldn’t come to my office, and I wouldn’t have any reason to come here, because before this morning, I didn’t even know you existed. So who’s going to stop the murder then?”

“It’s a conundrum, to be sure,” said Kairos, frowning.

That’s when we heard, very faintly, a child’s cry. Kairos looked up sharply and gasped. I followed his gaze and saw, across the lawn, a small girl flailing in the middle of a very large pond. Kairos was sprinting toward the pond now, and I followed him. He stopped at the water’s edge, clutching his hair in both fists. “I don’t know how to swim,” he shouted. The girl slipped beneath the surface.

When I was in college, I lifeguarded for two summers at a YMCA youth camp. Muscle memory kicked in and I dove into the water fully clothed, sprint-swimming to the center of the pond. I couldn’t see the girl anymore, but I remembered roughly where she’d gone under. I ducked beneath the surface, the water dark and murky and foreboding. I couldn’t see anything at all, but I kept pushing forward underwater, my lungs protesting the sudden deprivation of oxygen. I swept my arms in front of me in the hope of making contact with something, and finally, my fingers brushed fabric. I grabbed it and pulled it toward me, rising as fast as I could, the girl torpid and slack in my arms when I broke the surface. Kairos was screaming something, but I didn’t pay any attention to him as I clutched the girl to my chest and kicked toward the shore. I could tell she wasn’t breathing.

When I reached the shore, Kairos tried to take her, but I pushed him away, none-too-gently, and began chest compressions. Kairos batted at my arms, but I ignored him. After forty-five seconds, the girl sputtered, coughed up about three cups of water, and weakly whimpered, “Daddy?”

Kairos scooped her up into a fierce bear hug and looked at me in wonder. “I don’t know how to swim,” he said again.

“It’s a good thing I was here,” I said, and a sudden realization hit both of us at once. Without hesitation, Kairos unstopped the vial and drank its contents in one gulp. “Get her back to the house,” he said. “I don’t want her to see me when I… when I come back.” And then he disappeared, all at once, like a soap bubble bursting. I heard a soft “pop” as air rushed into the space he had just occupied. The girl blinked in confusion. “Daddy?” she said.

I reached for her hand. “My name’s Riley,” I said. “Why don’t you and I go for a walk?”

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