Prompt: A story beginning with a dying character, bleeding from the mouth, and staring at the knife embedded in his heart.

His research results would likely never be published now. He couldn’t finish the experiment, couldn’t document things properly. All his valuable data would be funneled into an autopsy report. Dr. Clyde Trapp was soon to be a corpse.

He knew this because he’d been required to train in medicine before he could move into his specializations of psychiatry and experimental treatments. In that training he’d learned much about the body, including the importance of the sliced pipes around his heart. He was collapsed against the side of his office door, a knife sticking out of the side of his heart. Blood pooled beneath him, a trail dripping from his mouth as well.

Those were crucial pipes, and there was nothing traditional medicine could do for him. That’s what he got for dealing in everything but the traditional. The experiments had been arranged four months ago, when he received word from a government body that he’d been approved as a researcher for a new technology, though he had not applied.

The machine in question was delivered to his office by a man who never removed his sunglasses. They did pay for a fancy new lock for his door before leaving. The machine came with instructions, explicit instructions, but only for setting up the device and explaining its purpose, not actually using it.

What came out of the triple-sealed box resembled a model of the human brain on a gray stand, with a small curved keyboard attached to the base. Upon activation the model glowed and emitted a small sound almost like a recording of a cooing pigeon. This was after the five hours spent examining the instruction manual.

The device had no official name, but its secret name was the Regretus. They did not include information on its mechanism or power source, but their intent was clear. The Regretus could map a human mind, record all its memories, and then explore them in great detail. This was not a simulation. It was a contained recreation of a past state of the world, perhaps a chance to do things over.

Dr. Trapp was instructed to create a log of his own mind, design several thought experiments, carry them out, and then report back. Reading the legalese only took four hours; the last one was spent staring at the page, fingers dampening it with sweat. It was all the implications, all the possibilities that froze him.

The cooing of the device, though soft, filled him with dread. He checked the door to make sure it was locked. He checked again. He looked out the window and then drew the curtains. Could he even do it? If he did, all his mistakes would be on the record. Everything wrong he’d ever done would exist in a government vault somewhere. Would such a legacy be viewed as honesty?

In the isolation of the quiet office, full of books with the names of other doctors egging him on, Dr. Trapp eventually put his hands on the device, let his thoughts flow into it. Across its lobes pictures formed. The images were familiar, but they grew unsettling as the hours wore on. He saw things in a different light. They were all a little off, which he initially attributed to the newness of the technology. Perhaps it needed to be adjusted to each individual, as everyone’s perception was a little different.

Therein was the answer. The way he remembered them consciously was wrong. He’d changed the lighting. He’d softened his own tone. In his memories he’d always made himself look a little more like a hero. The regretus corrected that bias before displaying the memories. That’s what was off. That’s what stung.

He told himself he was a doctor. The machine was right and he was wrong. This was supposed to be research, regardless of whether or not he was the subject. He took a deep breath and examined himself closely in the device. He was still formulating his experiments, this was just a survey, but apparently it was more than that for the regretus.

There was a version of Dr. Trapp in there, sick of itself now that it had a mirror. So many things he used to call mistakes, but that were actually just the deeds of a terrible man. He’d mistreated coworkers at his first job, when he didn’t have the safety of his own office. He’d lashed out at them like a cornered porcupine.

He’d lied. He’d stolen. The regretus saw it all, gave his conscience a cold rational weapon to hold. These memories of shame turned, looked at the man in his office, his new suit, his mustache that couldn’t hide his quivering lip, and was sickened by the sight. The regretus was a chance to change things. There was a memory of a knife, sitting on the kitchen counter, its blade covered in the thin reddish water of a freshly sliced tomato.

His shame took that knife and threw it out of the device. It landed in Dr. Trapp’s chest, snugly between two ribs, and rolled him off his chair. He sputtered and crawled for the door, leaking as he went. Right around the time he found the knob, he realized he’d lost a huge amount of blood. He put names to the parts of his heart that had been sliced open.

Even if he had the strength to crawl out into the hallway, nobody would be able to help him. There wasn’t enough time. This was an experiment, so the solution had to be experimental as well. He turned and put his back to the door. His knees were too weak to shuffle, so he had to drag himself back to the desk, past the regretus and its uninterrupted cooing.

He heaved himself into his spinning chair and up to the desk. There was his computer. With bloody hands he opened his Email and began to compose. His shame had done this to him. The shock of the curtain being pulled back and revealing someone who definitely was not a hero. If he could undo the self-hatred that had flung the knife, perhaps he could undo the knife. This was the new reality, where quantum technologies smashed headlong into the mind, so any treatment was worth a shot.

One by one he wrote out apologies, full of misspellings thanks to his bloody fumbling, and sent them off. He regretted those things. He really did. It wasn’t just his desire to live forcing him to finally admit it.

One last click. Now the whole world would know how he felt, but they wouldn’t be able to see the knife. Dr. Trapp looked down. He couldn’t see it either. The blood was gone. Slowly, he stood. When he was confident he had succeeded, he bolted over to the regretus and turned it off. The cooing finally stopped. He would send the government a letter, refusing their offer. He was not qualified. He was too emotional.

A week later he stared at himself in his bathroom mirror and saw how pale he looked. He felt the space over his heart. For the tiniest moment he felt a scar, but it wasn’t around long enough to be seen or proven. The previous night, in the middle of a sinful dream, he’d felt the blade again.

Was it always going to be there, just on the edge of reality? Was the stabbing permanent, and now just awaiting its catalyst? Every regrettable action could kill him, could strike his heart like it would strike the heart of others. Whether it was there or not, whether it was dangerous, whether it was his murderer or not, he felt it.