The gun is a People’s Army issue K-54, decades old and feeling worn smooth with age. He has never fired it but it is meant to be reliable. The silencer looks crude, almost home-made. Still, it will have to do. He wipes his hand on his trousers, cocks the gun and extends his fingers towards the code panel above the handle of the door leading to the private carriage. A tiny red light pulses slowly on the lock’s display.

They are approaching the highest part of the line, the Tanggula Pass, still most of a day away from Lhasa. The air feels cool and thin here, five kilometres up. Most people will be keeping to their seats, plugged into the train’s oxygen supply. Outside, the Tibetan plateau – a symphony of dun, beige and brown with a bitty overlay of early-summer green – has ridged and buckled over the last hour to create foothills that harbinge the crumpled parapets of low encroaching mountains in the distance.

The chief train guard had demanded a lot of money for the override code. It had better work. He taps it in quickly.

The tiny pulsing red light turns steady green. He feels himself swallowing.

The train rocks; the handle feels cold beneath his fingers.

And it begins with our young-sounding, young-looking, young-acting but in the end middle-aged friend Mr Adrian Cubbish waking up in his Mayfair home one London morning in – oh, let’s say late summer 2007; the routine is the same for the majority of days. He is in his bedroom suite, which takes up most of what used to be the attic of the town house. A light rain is falling onto the slabs of double-glazed glass which point at forty-five degrees to the light grey sky.

If Adrian were to have a symbol, it would be a mirror. This is what he says to the mirror each morning before he goes to work, and sometimes at the weekends when he doesn’t have to go to work, just for the sheer hell of it:

“The Market is God. There is no God but the Market.” He takes a breath here, smiling at his still-waking face. He looks young and fit, slim but muscled. He has tanned Caucasian skin, black hair, grey-green eyes and a wide mouth which is usually fixed in a knowing grin. Adrian has only ever slept with one woman who was significantly older than him; she chose to describe his mouth as “sensuous,” which he’d decided, after a little thought, was cool. Girls his own age and younger would call his mouth cute if they thought to describe it at all. He has a shadow-beard a night old. He lets his beard grow for a week or so sometimes before shaving it off; he looks good either way. He looks, if he is being honest with himself, like a male model. He looks just like he wants to look. Maybe he could be a little taller.

He clears his throat, spits into the glass bowl of one of the bathroom’s two sinks. Naked, he runs his hand through the dark curls of his pubic hair. “In the name of Capital, the compassionate, the wise,” he tells himself.

He grins, winks at his own reflection, amused.

And here, in a low-rise office suite in Glendale, Los Angeles, blinds slicing the slanting late afternoon sunlight into dark and shining strips draped across carpet tiles, chairs, suits and conference table, the noise of the freeway a grumbling susurrus in the background while Mike Esteros makes his pitch:

“Gentlemen, lady… this is more than just a pitch. Don’t get me wrong – this is a pitch but it’s also an important part of the movie I’m going to convince you that you want to help me make.

“What I’m going to tell you here is how to find aliens. Seriously. When I’m done, you’ll believe it might be possible. You’ll think we can capture an alien. What we’ll certainly be able do is create a movie that will capture the imagination of a generation; a Close Encounters, a Titanic. So, thank you for letting me have these few minutes of your time; I promise you they won’t be wasted.

“Now, anybody seen a full eclipse? Anyone been in the path of totality, when the sun is just wisps and tendrils of light peeking out from behind the moon? You, sir? Pretty impressive, sight, yeah? Yeah, mind-blowing indeed. Changes some people’s lives. They become shadow chasers – people who track down as many eclipses as they can, journeying to every corner of the world just to experience more examples of this uncanny and unique phenomenon.

“So let’s think about eclipses for a moment. Even if we haven’t seen an eclipse personally, we’ve seen the photographs in magazines and the footage on television or YouTube. We’re almost blasé about them; they’re just part of the stuff that happens to our planet, like weather or earthquakes, only not destructive, not life-threatening.

“But think about it. What an incredible coincidence it is that our moon fits exactly over our sun. Talk to astronomers and they’ll tell you that Earth’s moon is relatively much bigger than any other moon round any other planet. Most planets, like Jupiter and Saturn and so on, have moons that are tiny in comparison to themselves. Earth’s moon is enormous, and very close to us. If it was smaller or further away you’d only ever get partial eclipses; bigger or closer and it would hide the sun completely and there’d be no halo of light round the moon at totality. This is an astounding coincidence, an incredible piece of luck. And for all we know, eclipses like this are unique. This could be a phenomenon that happens on Earth and nowhere else. So, hold that thought, okay?

“Now, supposing there are aliens. Not E.T. aliens – not that cute or alone. Not Independence Day aliens – not that crazily aggressive – but, well, regular aliens. Yeah? Regular aliens. It’s perfectly possible, when you think of it. We’re here, after all, and Earth is just one small planet circling one regular-size sun in one galaxy. There are a quarter of a billion suns in this one galaxy and quarter of a billion galaxies in the universe; maybe more. We already know of hundreds of other planets around other suns, and we’ve only just started looking for them. Scientists tell us that almost every star might have planets. How many of those might harbour life? The Earth is ancient, but the universe is even more ancient. Who knows how many civilisations were around before Earth came into existence, or existed while we were growing up, or exist right now?

“So, if there are civilised aliens, you’d guess they can travel between stars. You’d guess their power sources and technology would be as far beyond ours as supersonic jets, nuclear submarines and space shuttles are beyond some tribe in the Amazon still making dugout canoes. And if they’re curious enough to do the science and invent the technology, they’ll be curious enough to use it to go exploring.

“Now, most jet travel on Earth is for tourism. Not business; tourism. Would our smart, curious aliens really be that different from us? I don’t think so. Most of them would be tourists. Like us, they’d go on cruise ships. And would they want to actually come to a place like Earth, set foot – or tentacle, or whatever – here? Rather than visit via some sort of virtual reality set-up? Well, some would settle for second-best, yes. Maybe the majority of people would. But the high rollers, the super-wealthy, the elite, they’d want the real thing. They’d want the bragging rights, they’d want to be able to say they’d really been to whatever exotic destinations would be on a Galactic Grand Tour. And who knows what splendours they’d want to fit in; their equivalent of the Grand Canyon, or Venice, Italy, or the Great Wall of China or Yosemite or the Pyramids?

“But what I want to propose to you is that, as well as all those other wonders, they would definitely want to see that one precious thing that we have and probably nobody else does. They’d want to see our eclipse. They’d want to look through the Earth’s atmosphere with their own eyes and see the moon fit over the sun, watch the light fade down to almost nothing, listen to the animals nearby fall silent and feel with their own skins the sudden chill in the air that comes with totality. Even if they can’t survive in our atmosphere, even if they need a spacesuit to keep them alive, they’d still want to get as close as they possibly could to seeing it in the raw, in as close to natural conditions as it’s possible to arrange. They’d want to be here, amongst us, when the shadow passes.