One starless night you take your dog out for a walk on the field behind your house.
It's late, you haven't been able to sleep in this heat, and you've started taking these late night walks with the dog.
Each night it's empty and silent, only a stirring of the long grass, but this particular night is different.
Above you, a plane unlike one you've ever seen seems to drift over you, as if it is scanning you. It's round, there are red lights flashing below it. It hovers above you and, incredibly, you see figures through a window on its bottom.
They don't look human. Huge buggy eyes and dark complexions, they are as enthralled by you as you are by them. And then the craft leaves, moves away to the trees, further and higher, until it's vanished.
After a sleepless night, you get up in the morning unsure whether what you saw actually happened. You haven't told anyone, maybe you'll tell your mate at the pub at the weekend, they won't believe you, but it'll be one hell of a story.
You get a knock at the front door and two men in black suits and black hats stand there. They tell you they're selling insurance, but they don't seem like the regular salesmen. Somehow they're in your house, sitting on your sofa and telling you the events of the previous night, in minute detail nobody but you could have known.
They threaten you, tell you to tell nobody if you value your security. They terrify you, and leave you sitting there shaking. Who were they? Where did they come from? How did they know?