Chaos theorists work forward from the principle they call "sensitive dependence on initial conditions." In other words, a very small initial difference many lead to an enormous change to the outcome. This principle is sometimes called the 'Butterfly Effect.'

-The Practical Skeptic (6th Edition), Lisa J. McIntyre (2013).

Gilly Hopkins followed the Doctor through the hallways and into a cream colored room with a clear tube in the middle that seemed to glow a diffuse teal. There were a set of metal stairs on the far end that curved upwards. The Doctor gestured for her to go first and, hesitantly, the albino complied. As her feet finally touched down on a hard, smooth floor, she looked up to see a place that could definitely be considered alien. Props for being prepared, she thought. But anyone could make a set like this if they had enough money and time on their hands. As she gazed about her, Gilly deduced that she was in the control room, if the giant console slap-bang in the middle of the room on the circular, top-most level of metal grating was any indicator. For a supposed space ship, it was surprisingly organic in appearance, lots of coral to go with the metal.

A bronze colored light was provided through the roundels in the walls, which meshed quite pleasantly with the soft teal light being emitted from the console. There were six coral support struts that looked somewhere between deer antlers and trees. The struts sprouted from the lower level of metal grating that seemed to be in the shape of a hexagon, which Gilly hesitantly stepped on, the grating being the only barrier between her and the cream room below. It continued to hold her weight and Gilly noticed that the level of grating she was on continued underneath the circle level of grating, becoming a solid sheet of metal as it bore all the wires and cables and tubes connected to the console.

Gripping on the railing, Gilly used it to guide herself around the upper-grating-level perimeter as she tried to take everything in at once. She noticed an out-of-the-way metal ladder which lead to a metal grating walkway above her head that hugged the wall. There was a gap in the railing, and she stepped up to the next level, now close to the console itself. It looked…old, for lack of a better word. Stone supports sectioned the console into six separate panels, while the base and trimming of it was made of coral. The teal light was emitted through what appeared to be frosted glass, and scattered on top of it were various buttons, levers, knobs, and notches. There were also devices, switches, gizmos, and cranks. There was a monitor and a keyboard situated almost randomly on one of the panels. The screen frame had several sticky notes attached, but instead of words, there were complex and simple circle designs.

All in all, it was very impressive, which Gilly didn't withhold from the Doctor. He seemed to preen at her words of praise concerning his ship's console room, looking very smug and proud. "And that's not all," he crooned. "Did I mention we can go anywhere in space and time?" The man seemed barely able to contain his gleeful excitement, practically skipping up the two grating levels and over to the console panel across from hers. His grin was wide and eager as he asked, "What's the one place you ever wanted to go to? The future? The past? A distant planet or somewhere close to home? Somewhere that could only have come out of your wildest dreams or maybe somewhere that you would have never even begun to think of? Eh? Your choice. Where do you want to go first?"

The ex-mortician could only blink at him dumbly. "Blame the radiation if you want to," Gilly eventually began after a long moment. "But my mind's completely blank." The Doctor's face vaulted in disappointment. "Really, it's all kind of on the spot, can't think of anything, nothing comes to mind… Probably doesn't help that my mind was blown from this mesmerizing environment."

"Nothing? Not even one, small, teensy idea?" The Doctor prodded.

"No, sorry. I mean, I still can't quite believe we're in a time machine or whatever. You're the pilot, put it on random or something. Impress me." Honestly, she just wanted a chance to see if he really was as mad as she thought he was. She may have been able to give him the benefit of a doubt with the whole space ship idea, but time travelling? Seriously, a time machine? What a terrible lie. The amount of paradoxes alone it would cause-

Her train of thought was entirely interrupted when the whole area gave a violent shudder. With a screech of fear, Gilly clung to a support strut, her heart beating frantically. Words failed her as it felt like an earthquake passed through, something that she was for certain wasn't common in Europe. The Doctor ran around the console, flipping switches and yanking down levers, pressing buttons here and there. It seemed like it should be more than a one-man job, and this opinion was only strengthened when he used his foot of all things to kick at a wayward switch that was currently too far from his grasp. It was only when he brought out a mallet to hit the console that she began to seriously fear for her safety. Did he actually pass a driver's test for this? Do they even have driver's tests for time machines? They must have, they better have, or I'm doomed…

Eventually, they came to a shuddering halt, but Gilly refused to release her cicada grip on the coral support strut, in case it was only a temporary relief. The Doctor regarded her with some amusement. "It's safe to let go now. We've landed."

Within an air of wounded dignity, she carefully unlatched her limbs one after the other from her safe haven, tentatively standing on the ground with one hand on the support strut. She eyed the floor at if it were a wild thing. The Time Lord responsible for all her troubles watched her, completely entertained by her actions. He never had a companion act like this before, and it was beyond hilarious to see her so off-balance on her first trip. He didn't like cats much in this regeneration, but he was greatly reminded of one in a positive sense as he watched her attempt to act as if nothing had happened and fail.

"Don't worry, you will get into the swing of things soon enough," he told her. It wasn't his intent to sound patronizing, but that was exactly how Gilly took it. She sent him a mutinous glare that the Time Lord was seemingly impervious to as he sauntered towards the door, grabbing his coat on the way out. The young woman was left with little choice but to stumble after him and into the outside world. The door shut behind her firmly and locked, providing a solid surface for her to stumble back against in shock. They were most certainly not on Earth.

They were on a beach with white sand reminiscent of the picture of the Bahamas that she saw on a magazine. Sea-green waves rolled continuously onto the shore, crashing into it and reluctantly slithering away before returning in a never-ending cycle. It was late afternoon and warm, almost tropical, despite the breeze that tugged persistently on her loose hair. Faintly, Gilly regretted that she didn't bring her sunhat, she would get sunburned out here. Her glasses tinted themselves darkly to block out as much as the brightness as they could.

To the Doctor and Gilly's left was a large cliff made up of different apartment blocks, terraces, and observation decks, all built to get a view of the ocean. They were stacked together like puzzle pieces, rising high into the sky. Beyond them, the occasional tower or spire would peak above, hinting at more to see. None of the buildings were in any designs of Earth architecture that were familiar to the woman at all, which might have been clue enough. The biggest hint that she wasn't home, however, was that the sky was a shade of green that reminded her of those obsessively maintained laws in suburbia, a thick green that was almost bluish in color, it was so rich.

The Doctor took in her expression of unconcealed awe and surprise with great relish, as if he had missed it. Only too happy to, he offered an explanation for the sky's odd color without Gilly even needing to ask, "Green skies like this happen when you get a lot of water vapor in the atmosphere. On Earth, you get them too, but only if a tornado's on its way. Currently, we're on a planet nestled deep in Galaxy Seven, or the Sculptor Dwarf Galaxy, as it used to be known until the tourist board changed it. We're almost exactly 290,000 light-years away from Earth, and, incidentally, it's almost the year 290,009. If we had a really powerful telescope, we could look through it and see the Earth in the year 2009!" His grin was smug as he rocked back on his heels as if to say, 'Ha! I told you so.'

"Wow," was all Gilly could say. She sat down.

"Alright?" The Doctor asked, a concerned look briefly flitting across his face. "Are you feeling ill? We can go back if you—"

"No," the ex-mortician immediately refused, sick of being stuck inside for what felt like forever. "I just… need to process this. I'm not on Earth."

"No, you're not," the Doctor agreed.

"I'm no longer in the year 2049."

"No, you're not." But the Doctor did store that piece of information away for later. she was, apparently, not from 2011 like he assumed when he first met her.

"The sky's green."

"Yes, it is. Getting the idea, now?"

"Oh yeah, like a brick to the face," she informed him before forcing herself into a standing position, dusting the sand off of her leggings and blue polyester dress. She shucked off her ballet flats and held them in one hand, gesturing with the other for the Doctor to lead the way. "After you," she told him, wiggling her toes in a thrilled manner at the sensation of the sand on her bare feet.

She had to admit, this was entirely impressive and utterly impossible to fake. She curled her toes for a moment in unease before, taking a steadying breath, she pushed off the TARDIS door she had been leaning against for strength and followed the Doctor. The beach was beautiful and tranquil, giving the impression of an untroubled place. Gilly found herself beginning to relax, a smile forming on her face. She had been so apprehensive about the 'trip' that the Doctor had mentioned to her, especially when he tried to explain to her earlier that his space ship was a time machine. And that he was an extraterrestrial.

She had, quite frankly, thought he was nuts, and, like the idiot she was, she had challenged him to 'prove it'. So here they were, not on Earth, on a deserted beach, wandering around the perimeter by the rolling waves and enjoying the nice weather. Well, more like Gilly was enjoying the nice weather, because she had been convinced that she would never see the light of day again. The Doctor was enjoying the look of bliss on his new companion's face, which, if Gilly had noticed, she would have found unsettling and creepy on so many levels. But, she didn't, and was trying to figure out a way that she could try to weasel out another trip to some other unearthly place before he took her home.

Suddenly remembering herself, she stopped abruptly, causing the Doctor to tense and stop too, a look of wariness developing on his face as he gazed around, trying to ascertain the reason for her sudden change in behavior. There was nothing he could see. The beach was completely empty, the sand scrubbed clean of almost all evidence that people had come down here to sunbathe, build sandcastles, and read bad books. The beach was broken up by rows and columns of metal posts, all that remained of what had used to be windbreakers, boardwalks, and piers. The metal posts that remained were terribly corroded by the saltwater, and the sand had drifted up, half-covering everything. There was no sound except the wind and their brea—

Click.

The Doctor whirled around, expecting the worst: a gun, a malevolent creature of some sort… But no, it was only Gilly who had taken out her camera and was taking a careful picture of the ocean and green sky with an almost reverent look on her face. Turning around, she took another picture of the cliff-sides before turning off her camera and allowing it to settle back to where it originally rested against her lower torso. She caught the dirty look he was giving her for startling him, because there was no way that she could actually scare him, since never before did he have companions who took pictures.

She scrunched her face back at him. "Well, sorry," she said defensively, even though he had yet to say anything to her, but he supposed that his expression had done the talking for him. "Us humans get faulty memories when we get older, plus my vision's starting to go. Back at home, I heard they were coming up with new technologies every day… I just wanted to have a picture of this place, in case they invent something to fix my sight. If not, well, I'll have something to show my kids anyway."

The Doctor went cold. "You have kids?" He didn't even consider. The possibility had been so far from his mind, and with her this young, likely around her late twenties, the children would be still dependent upon her, especially if there wasn't a father in the picture—

"Huh? Oh, no, not yet. Someday, maybe." She gave a silly smile, her thoughts obviously elsewhere and she, therefore, didn't noticed the look of unadulterated relief on the Time Lord's face.

Well, that's one less problem, he thought to himself. The biggest problem was, however, he still didn't break the news to Gilly yet. The problem of her never being able to get home. The Rift didn't just drag her thirty-eight years into the past, it had also brought her from another dimension entirely. There was no way she would ever be able to get home, what Rose had done with the dimension cannon had been an exception, the only exception on extenuating circumstances. Not that it mattered, he thought bitterly. She ended up being stuck in Pete's World with the Metacrisis, anyway.

"So, where are we, exactly, besides Dwarf Galaxy Seven?" Gilly asked.

The Doctor, thankful for a distraction, corrected, "It's called either Galaxy Seven or the Sculptor Dwarf Galaxy, not—"

Gilly made a dismissive sound. "I was close enough. You knew what I was talking about."

Rolling his eyes at her childishness, he answered her original question, "We're by the ruins of the city of Arcopolis. It's on top of the cliff. We can't quite see it at the moment because of the tourist district blocking the view."

"Oh, that must've been those towers I saw," she realized.

"Down in one," the Doctor agreed.

"I've always wanted to see the ruins in Greece," the albino reflected wistfully. "But I'm sure this will more than make up for the lost opportunity." At the brunette's questioning look, she explained, "It was either that or the UK, and I couldn't afford a tour guide for either, so I had to go with the English-speaking countries."

Bobbing his head in acknowledgement, the Doctor once again continued his trek along the beach, only this time heading towards the cliff-side. Gilly scrambled to keep up. "Well, Glenda Hopkins—"

"—it's Gilly—"

"—I'm about to show you a city that's been completely deserted for over fifteen years," he continued on, mindless of Gilly's irritated correction. The two of them approached the walls of the cliff where there were the old ways of transportation, namely anti-gravity lifts, the tubes translucent and clear to display the glorious view for the people's journey to or from the beach. The Doctor went up to the blocked off entrances while Gilly wandered off to find a set of stairs. The heavy doors refused to budge for him, and, reluctantly, he gave up, striding after the young woman who was starting to get a bit too far way.

It took maybe ten minutes or so before they found a spiral staircase that led up a couple of levels. They went up it only to find themselves at a dead end, their path being blocked by a large, rounded window. Gilly, assuming they would get no further, started to descend several steps before she heard a queer sounding warble and the shattering of glass. She whipped around to see the Doctor stuffing something inside of his pocket and entering the through the threshold of the non-existent glass barrier.

"Was vandalism really necessary?" The albino groaned in exasperation.

"Well, it's not as if anyone's here to care," the Time Lord retorted. "Watch your feet."

Huffing, Gilly stuffed on her ballet flats and gingerly walked through the glass into the flat. The space was large and open. The women would have called it airy if it wasn't so musty from fifteen years of abandonment. Sectional sofas littered around what had to be the living room, plush throw blankets and pillows placed randomly on them. A small robot of some kind was in the middle of the room that looked like a mix between a Roomba 880 and Baymax. Several rather beautiful paintings were placed on the otherwise-bare walls, their colors fading from being in the sun for so many years. However, the paintings were the only colorful colors in the room, the rest was all monochrome, black metal, and dark glass, certainly fitting in with the idea of it all being futuristic.

The Doctor had moved towards the back wall where another window was located, studying the view in front of him featuring the city. More than a little eager to see some actual ruins, Gilly was quick to join him and take in the view herself. Her first impression was that the two of them had somehow been shrunk to the size of Barbie dolls and placed within a child's city made of building blocks. There were towers in the shape of corkscrews, giant sphere buildings, domes on top of single and skinny rectangular columns, pyramids, trapezoids, and more, so much more. Each building had walkways and metal roads that interconnected with them like someone had put black and silver streamers on the children's building block city.

"Wow, and I thought the physics teachers back in college were impressive with their demonstrative precarious structures," Gilly finally commented.

"The citizens of Acropolis had centuries to get everything down to an art form." The Doctor picked up an abstract-shaped, metal piece that looked like it belonged in a museum. "Every curve, every line, every angle in this city has been calculated to five decimal places. Most civilizations, if they last long enough, can reach the stage that this builders had. Used to be a brilliant place to live, very peaceful."

"Sounds like Utopia," Gilly commented.

The Doctor winced, unwanted memories being stirred from the very word. Reluctantly, the Doctor moodily said, "…I s'pose…"

Gilly looked up in surprise at the sound change of attitude, but the Time Lord refused to meet her questioning gaze, his own stare caught by something else entirely. She followed his line of sight and cringed. There was a giant black structure that dwarfed the rest of the buildings easily. It was an eyesore, in the general shape of a pyramid but covered in sharp angles and cruel-looking spikes. It was terribly ugly and utterly alien in appearance next to the smooth and dainty structures the rest of the city presented. As she looked upon it, the malevolent structure filled her with a sense of dread.

"Wh-What is that?" Her voice quivered despite her best attempts to hide her unease.

"The Fortress," came the quiet answer. "And the reason why this city, this… Utopia has become ruins and devoid of life ever since fifteen years ago."

"It's unsettling," she told him. "Like it can almost see me…" The Doctor had nothing to say to that, and a silence stretched between the two of them, broken only by the distant sound of the sea, so far away from them now. It was eerie here in the desolate city where millions of people once lived, where it was once filled with sound and life. Now, there was nothing.

It was a long moment before the Doctor asked, "So you mentioned that you've been meaning to get up close and personal with some ruins?"

A/N: This chapter is called 'The Initial Difference' for a very good reason. This is where things will actually begin to change, that cannon will begin to bend and alter itself as you will see in the next chapter.

As a reminder before anyone asks, yes, this adventure is cannon. It is a 'Doctor Who' book called 'The Eyeless' by Lance Parkin.

Anyway, Happy Easter, I guess.