They’re watching you.

Clouds of smog roll in on the evening breeze, obscuring the view to less than a dozen feet, and filling the air with choking fumes. In the growing dusk, brought on early by the opaque clouds, lights begin to come on in this part of The City. Due to the rapid expansion of the world's population, The City now covers two thirds of the Earth's landmass. The City has spread as deep and high as it has wide. Deep beneath the Earth's surface, sprawling networks of tunnels and catacombs are home to a thriving criminal underworld, full of potent synthetic drugs, a single dose of which can keep a man in hallucinations for years, deadly faction feuds and infighting, and illicit bionic body modification parlours, preying on the disenfranchised who may be prepared to take any risk for a shot at escaping this hell.

The streets at ground level are normally empty. The toxic smog, full of heavy metals and poisonous chemicals can roll through with less than a moment's notice. Few take the chance of being caught out in it, and fewer survive. If one was to take stroll through this apparent ghost town, one would likely notice the occasional movement in the shadows, near long-boarded-up storefronts and abandoned public fixtures. There are those who live in this wasteland. Few live long. Most are cast-offs of the criminal underworld, and would-be entrepreneurs from the bustling hive of activity above whose luck ran out and whose debts caught up with them. The few denizens of this place who last more than a week become hardened veterans of the shadows. They know where to find food and air, and how to move about unobserved by the uninvited voyeur. If you venture here, take care to look out for these folks, for an encounter with one may be your last.

Above the smog-filled wastelands, rise innumerable towering buildings with massive glass windows. These buildings are packed as tightly as the streets below will allow, and many join up in mid-air, forming a continuous aerial thoroughfare. Within this vast expanse of interconnected buildings, the great majority of The City's residents live, work, and die, many never setting foot outside even once. A well-designed internal transport network removes the need for these people to leave this place, or even think about the outside. This is the domain of the business magnates, a small number of wealthy men who own everything, and care about no one other than their own pockets. If one cares not for their greedy rule, the alternative is to take one's chances on the streets or the criminal underworld below.

In this world, population growth has not just been fuelled by the natural reproduction of humankind, but by unprecedented technological advances as well. Robots, or "synthetic humanoids," as they are commonly known, have become indistinguishable from real humans. Researchers were proud when they first made a robot that could pass as human, but soon they lost track of how many they had made. They say the computer with the records crashed, destroying the hard drive, and the backups were lost in an unfortunate fire on the same day. Same say this is too much to be coincidence.

To begin with, the synthetic humanoids were easy to catch if you had a good eye and knew what you were looking for. There were tells. But over time, they seem to have learnt not only to build copies of themselves, but to improve and adapt their programming with each successive generation. The one thing they always struggled with was romance. It was their greatest tell. For many years, one merely had to make an advance and you could tell whether you were interacting with a human or a synthetic by the reaction. Sadly, over time, this tell too was engineered out to near perfection. But one tell still remains. We call it The Test.

~~~~~

As Justin walked along the corridor, he paused. He had the misfortune to be walking on the lowermost outer corridor on a connection bridge. He hated looking out the window, but he hated his job more. So he stood there, and steered at the smog rolling in. As he watched the toxic clouds gradually hide the grey streets below from his view, he pondered on the news that had been announced that morning. Less than a month ago, there had been an election, an impressive feat for a collection of people the size of The City. He didn't really care who had been elected. They were all puppets of the business magnates, as far as he could see. Already though, there were policy changes. This morning, they had announced a new law that all public servants were required to be chaste. Justin thought it was strange law, and wouldn't really have cared, except that it seemed to have put his boss in a particularly bad mood. Justin was pretty sure that his boss was human, as he couldn't imagine a synthetic having such unpredictable mood swings, but he hadn't done The Test to confirm, and really didn't feel that he wanted to. There were murmurings today that something was wrong, but he didn't feel that it concerned him, so he ignored the rumours and continued on his way to work.

Like most residents of The City, Justin was happy enough with his life. He had a job that paid enough to buy food and clothing for himself, his wife, and his two children. He had a family, and he had a roof over his head. He was also not a criminal, or stuck on the streets outside. Life wasn't glamorous, but it could be much worse. He had almost married a synthetic. He cringed internally every time he thought of it. She had deceived him, persuaded him there was no reason to do The Test until they were wed. He had learnt his lesson from that. He knew his wife was human, and he had made certain he did The Test before he got too far in.

As he sat down at his desk, a news article flashed on his screen. He decided that he might as well check it out, as it meant that he could avoid doing work for a bit longer. As he opened the article, a video clip began playing. A rather large man, in a ridiculously formal, tailored suit, and gold earrings was talking. Justin recognised him as the business magnate who owned the company he worked for. Normally, this fellow was busy gloating about his record profits, but today he seemed agitated. Justin started actually listening. The fellow was concerned that synthetics were taking over the government. Justin found this rather hilarious, as this fellow and his compatriots were really the only ones in control, anyway. But the more he listened, the more Justin realised what the problem actually was.

~~~~~

The only way to be sure you have found a synthetic humanoid is to sleep with it. People say it's not bad, just different. This is The Test. If you don't want to sleep with it, you can take it to a testing house. You can let someone else sleep with it and tell you. But beware, if you go to a testing house run by a synthetic humanoid, you may not get the answer you are looking for. You may need to Test the tester.

~~~~~

Justin didn't feel like going to work. He was still thinking about the video clip he'd seen two days. He'd been unable to concentrate at work yesterday, especially after discovering that he couldn't find the article when he went looking for it again to show his wife. He had a strange sense of foreboding, and he didn't like it. Trying to take his time, he deliberately took a longer route through a major shopping zone. He spent as much time as he could justify gazing at each window and deciding what he'd spend his money on, if he ever had enough for more than the bare basics. He decided on a nice, striped tie for himself, and a new set of painted china dinner plates for his wife.

As he moved on, he passed by Madame Toufrae's, the most reputable testing house in this part of The City. Madame Toufrae herself was standing outside, and he offered a greeting as he went past. She raised her hand to return the greeting, and Justin hurried on, now concerned that he would get in trouble for being a little later than his usual tardiness. Halfway across the the bridge corridor, he realised something. As far as he could recall, Madame Toufrae always wore gloves. Generally, elbow-length white lace. Today, she had not had gloves on. He dismissed it, and carried on. People were entitled to try new things and wear whatever they wanted. It was none of his concern.

~~~~~

No one really knows how the synthetic humanoids were able to resolve their shortcomings in romance. One theory suggests that they analysed human-produced media and altered their behaviour to align with our idealised romantic interactions. Opposers of this theory maintain that this would not have allowed them to so swiftly and transparently integrate into society, as our media is too unrealistic. Another theory suggests that they instead fed us with their own ideals so that we came to expect them to interact in the way that they do, and mirror it ourselves. The final theory, of those that seem likely, is that they achieved it by trial and error. By engaging in dating practices at scale they could have collected enough data to improve their performance and gather more data with another iteration. This seems the most likely.

We suggest to you that if you venture into our world, take care who you trust. The synthetic humanoids are their own master. We no longer know what they desire, or who among us may be one of them. How you choose who to trust is your problem, not ours. Good luck.

~~~~~

When Justin arrived at work the following morning, the normally dreary office was abuzz with muttered gossip, and sideways glances. He tried to find someone who would tell him what was going on, but everyone seemed too preoccupied to talk to him. He sat down, rather annoyed, at his desk, and turned to look at his monitor. There, in front of him, was another news article. The article informed him that, as much as synthetic humanoids were normally indistinguishable, you could sometimes tell when they were impersonating a specific human. It suggested to look out primarily for subtle changes in their dressing patterns. And then the article abruptly disappeared. And that was when Justin realised why his wife had gone to work that morning in the dress that she hated....