All the loose ends

1
It was horrible. He stumbled into the room, led by an orderly. Staring me in the face, he radiated a nameless existential terror. From his mouth spewed a series of incoherent exclamations.

"I can't... you... oh god... how can... I... uh... Christmas!? Why did..."

I stared at his face. It was me, all right. He was trembling uncontrollably. Finally he screamed.

"SAY IT!" he bellowed.

"Okay, he's seen enough." MacAllister rested a hand on my shoulder. "Come on," he said, and led me from the room.

2
"This is the dossier," MacAllister said, holding out a hefty file. "It's all in here. The exact times and dates of the attacks, contemporary maps of the locale. You'll be equipped with an outfit before transit."

I stared at the dossier. "How will I get back?" I asked.

"For agents travelling to the far past, there is a one-time use return beacon. You can activate it at any time and it will be detected by our facilities. You will be instantly returned to a point we specify - usually, the day after the initial departure."

"How does it work?"

MacAllister shrugged. "How does a microwave work?" he asked.

"It exploits the resonant frequency of water molecules to generate heat," I answered, even though it was obviously a rhetorical question.

"And our technology exploits the non-linearity of time. But I personally couldn't build one. Or a microwave."

I didn't press the issue any further.

"Now," he continued, "it is imperative that you are careful whilst on the mission. Do nothing to arouse suspicion amongst the locals. Above all, remember that if anything happens to you then you are on your own. We can't help you. There is no guarantee of safety at this point. We won't know if the mission is a success until the moment the return beacon is received, or isn't. If you don't return to that point, we'll know you never lived to activate it."

Hating to ask more questions, I did so anyway. "Why can't you set the beacon to return me to just before I set off? That way you'd know in advance whether to send me."

"Because maybe when you didn't come back it would just be because we never sent you in the first place. Because you didn't come back." MacAllister sighed. "Anyway, we try to avoid overlap because of the psychological implications. You should know all about that. We all know about it."

3
I couldn't find the strength to resist as the orderly led me out of the room. I knew I'd have to wait for MacAllister, as he was still in the other room putting me into the machine more or less against my will. I could see each footfall before I took a step. Everything felt distant.

Eventually MacAllister arrived for the debriefing.

"That was your first experience of time travel. Don't worry, it gets easier."

I opened my mouth to speak, and found that I was crying.

MacAllister tried to look reassuring. "Don't worry. I know it's hard because we've all been through it. But your psych screening tells us that you'll get through it. You would never have got this far otherwise."

I struggled to regain composure. "Why... why..?"

"Why do we do it?" he finished my question. "It's to teach, by example, something about the nature of time travel. What happens when you meet yourself? What you just experienced, that's what.

"You'd have thought, wouldn't you, that the biggest danger of time travel was the creation of a paradox? I don't need to tell you - you kill your own father, you stop an assassination, you change history somehow. Well, that would be the easiest way to do it - to meet yourself. Imagine, you meet yourself and have a conversation. Then you go back in time to have the other half of that conversation, only this time you say something different. A paradox - impossible.

"Only it really is impossible. The only possible outcome of that meeting was exactly what happened. You had no choice but to repeat the same sequence of words you had heard."

I felt sick. "But..."

"Why Christmas?"

"What?"

"You said it, back there. Christmas. Why?"

I stared back at him.

"Because you heard yourself say it. But why that word? What if it had been another word? House. Furrow. Guacamole. You would have had no choice but to parrot it. So who chose what you had to say, if not you?"

"I don't... I don't know."

MacAllister smiled gently. "That's what's you lose in time travel. The illusion of free will. I mean, it was never there. I mean, we all liked to imagine it was. 'Oh, if only I'd done things differently. I could have done this, I could have said that.' Well, you can't. How could you? There's only one possible reality, and that's the one that happens."

4
I was applying for a job in the police force when I got the invitation. They told me my psych evaluations suggested I might be suitable for work in a pioneering branch of forensics. It sounded intriguing, so I put myself forward. It was only as the application progressed that I learned more about the nature of the job. The idea was to use time travel to finally put to bed the great unsolved crimes of the past. Where, even in retrospect, with all the evidence at hand, no one individual could be unambiguously identified as the culprit. As a last resort, armed with the knowledge of where and when the crime took place, we could travel back and witness it for ourselves.

Of course none of it could be stopped from happening, but what a triumph of police work! An end, finally, to the mysteries that had tantalised generations.

5
For a moment, I could see everything. I could witness everything from the dawn of time to the end of the universe. But it was too big to see any details. Once time had regained its linearity, what I had seen became impossible to describe, and after a few seconds I realised I couldn't remember what it had looked like.

6
There were five people on the debriefing board. Dempster, MacAllister, and three others I didn't recognise - one man, two women. Their features were difficult to make out in the dim light.

"Deliver your report," one of them barked.

My throat was dry. "I... I arrived in time to familiarise myself with the area. I tracked down the victim at her house. It... everything was as it was in the dossier. She left the house shortly after eight in the evening... the last time she was seen alive." I paused. "Could I have some water?"

"Continue," Dempster murmured.

"Okay... I tracked the victim to the alleyway where her body was found. She took a shortcut by that route. And I waited at one end, presuming the murderer to be either concealed in the alley or lurking at the other end. My plan was to follow him after the attack until such point as I could make an identification, but..." I trailed off, feeling momentarily breathless. None of this seemed real.

"In your own time." A female voice.

"There... there was no murderer! She just carried on through the alley! And I don't know how, but I thought, no, I've read the file, you die here tonight! And so I ran down the alley after her, and she turned round when she heard me, but she couldn't defend... I mean, I've had all this training..."

It was as though I was watching myself. I felt bad, but I could only recognise this bad feeling inside myself. I couldn't really feel it. I was just reading a script, anyway. I was reading a script the whole time.

MacAllister nodded silently at the man whose face I didn't recognise. "I think we have enough," the unknown man said.

7
"What will happen to me?" I asked MacAllister as we walked down the corridor. "How much trouble am I in?"

"You're not in trouble," he replied. "You weren't responsible for your actions. None of us are."

"But I killed that woman. And I've read the newspaper articles. I've read the books theorising who did it. And it was me."

"Listen," said MacAllister. "You know how many of the crimes we investigate are perpetrated by our agents? It's not all of them, but it's a lot."

"What I don't get," I continued, "is why you had to make me meet myself. To prove a point? What was the point? If I hadn't had to do that, then I wouldn't have this feeling all the time."

MacAllister shrugged. "I don't know why. Why do we do anything? But we had to do it."

"Why was this department set up?"

"Why did you say Christmas? Everything happens for a reason, but it's not for us to know why. How can we? We just play out the role apportioned to us. You should be grateful. At least we have the privilege of knowing how it all works. And that feeling you describe; it never goes away, but eventually you learn to live with it."

I said more words to MacAllister after that, and he said more back. There didn't seem much point, as we both knew what would be said. But we said them anyway.