I'm going to twist this a little bit. 20 years is a really long time to change the future so I'm going with 1 hour.

"So, this is it. This is the moment you've been training for the last five years." General Stam said.

"Yes Sir." Replied Chase. A gaunt, but strong looking man with olive skin. Chase had been picked from thousands of unknowing candidates because of his looks and raw intelligence at the age of 10. Groomed to be the man who changed the past and in return, changed everything that came after.

Everything about Chase had been molded in the previous five years. His physique, skinny but strong from manual labor. He was almost more fluent in ancient Greek complete with a dialect matching that of the Alexandria region than he was in his native tongue. His hands callused to match those of the people he would soon be around. Beyond how he looked, he was trained to be extremely charming and influential even for his young age.

Chase had been made into the perfect impostor. Made to blend into a time and place that was hard but exciting to imagine, 65AD in the Greek city of Alexandria. All for a 1 hour shot at changing the future.

General Stam cleared his throat. "Alright Chase, lets go over it all one more time."

"I've got it, really"

"One more time..." Stam said with an authority that Chase chose not to challenge, even though he knew, and had known for awhile, that he was the one that mattered here.

"I'm going back to Greece, Alexandria to be exact. The year I'll arrive is 65AD at roughly 7am. I know I'll appear just outside the city, away from the main roads so I'm not likely to be seen upon arrival. I know the exact layout of the entire city and am to head directly to the Musaeum and find Hero of Alexandria who will be teaching his class on pneumatics and showing them his latest invention before he displays it publicly, the Aeolipile. I should have about 35 minutes left by then."

"Then?"

"Then you or your scientist" he frustratedly waved off towards a domed building with the back of his hand "can't give me any solid answers so I have to wing it."

"NO! YOU KNOW WHAT TO DO!"

Sigh... "Because we don't know when class gets out I have two options. First, if I catch him alone, I ask about his machine, working the conversation towards attaching a gear or rope to the side of it, connecting it to a wheel, maul or anything that was done by hand but can then be done mechanically. If possible I try to make it seem like it was his idea. Then I leave and find a private place to vanish."

"And if class is still in session?"

"Then I'm an arrogant asshole. I walk past the door, act like I take notice and scoff at the uselessness of his "toy" then in a very condescending way I say how I would at least make it do something, maybe put something on the side to make a fan. We know enough about Hero to know even this unpleasant meeting might plant the seed. He's not the kind of person to let pride or anger overcome a new idea. Then I leave and find a private place to vanish."

"What happens if this plan works?"

"The first steam engine is built in 65AD. A crude version of the industrial revolution starts 1665 years early."

"What happens if this plan fails?"

"Nothing. As far as we know time can only be torn once. We fail."

"Good... You have it all down. Chase, you are going to accomplish this mission."

"Yes Sir."

Chase stood inside the machine, wearing his toga and sandals. As the power from a miniature nuclear reactor pumped energy though the 3 foot wide cables that curved out of the walls, disappearing under the grated floor the device turned on and all that happened was a hum. No flashing lights, no spinning arms just a semi-loud, annoying hum. Chase stood on the platform wondering if the time machine was broken. Nothing but this hum, he thought? This can't be right. Something mus

And mid-thought, he was outside the walls of Alexandria. No jarring feeling, no nauseousness. Just there. It was pretty anticlimactic.

Following his mission Chase did exactly as was planned. When he got to the Musaeum luck was on his side and Hero was in the classroom alone looking at his invention. They talked and Chase blended in perfectly. He did his job perfectly. By the end of the conversation, as Chase was walking out the door, Hero was already pulling out his tools.

"Four minutes" he said out loud. He knew right where he was going though, four doors down, on the left was a hallway that led to a storage room archaeologists had determined. He turned the corner, running into a man that must have been 6'5 and made of solid muscle. He was wearing the right clothes but definitely did not fit in. Besides his size, he had perfect teeth, flawless skin and an all about perfectness in every small detail one could imagine.

"Hello Chase, It's an honor to meet you. I'm Aesop. I'm here to pick you up."

"W..What? How do you know me!?"

"Haha, your mission was very successful. More than you can imagine but that's what I'm here for, to show you."

Chase began to panic, this was never part of the training. His time should have expired, why haven't I gone home, he thought.

"Yeah.. About that. We accidentally broke your way home when we invented time travel. Your way worked but it was extremely crude. When we broke the time space continuum it erased the path back. Think of it this way, you made a dirt path through time, we accidentally built a how do you say.. highway, over it."

"So I can't go home? And how did you know what I was thinking?"

"I can take you back to the time you knew as home but you wouldn't recognize it. All the people you knew never existed or aren't who they were."

"Then how am I here?"

"The machine you used to come back doesn't matter. The dirt path you made with it does. Once you stepped outside of time it didn't matter if the machine was even built, you were already out. I'm not a scientist and that's really all I can explain about it. I can take you to people who know the details of the quantum mechanics behind it all but I have to tell you, they are a little.... Off."

"How do you know all of these things about where I'm from, the machine I used and the people I know if they never existed? And how did you know what I thinking a second ago?"

"I know because you know." Aesop said, tapping his own temple. "We have come a long way since the time you knew. Now, would you come with me? You are a legend in my time. All children learn about you in school. Our main time displacement complex even carries your name."

"Yeah.. I guess. Where else am I gonna go."

"Hahaha, ohhh just about anywhere you want! You're just going to have to see my.. your new time, for yourself."

"Ok, lets go. What year are you from?"

"896"

"The middle of the dark ages?"

"Yeah, I saw that in your mind. Damn. You really did change the future."

As his last word was spoken the hallway that had just held two time-travelers was empty once again.