'Before you take me up to bed, will you tell me a story?”

“Do you actually need me to take you up to bed?” I asked the boy.

He thought for a moment. Then, with intense seriousness, “Yes, actually I think you do. It’s because of, I’ve finished my homework, and so it’s my bedtime, and I am a bit scared. Not very scared. Just a bit.

“But it is a very big house, and lots of times the lights don’t work and it’s a sort of dark.”

I reached over and tousled his hair.

“I can understand that,” I said. “It is a very big old house.” He nodded. We were in the kitchen, where it was light and warm. I put down my magazine on the kitchen table. “What kind of story would you like me to tell you?”

“Well,” he said, thoughtfully. “I don’t think it should be too scary, because then when I go up to bed, I will just be thinking about monsters the whole time. But if it isn’t just a little bit scary then I won’t be interested. And you make up scary stories, don’t you? I know she says that’s what you do.”

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“She exaggerates. I write stories, yes. Nothing that’s been published, yet, though. And I write lots of different kinds of stories.”

“But you do write scary stories?”

“Yes.”

The boy looked up at me from the shadows by the door, where he was waiting. “Do you know any stories about Click-clack the Rattlebag?”

“I don’t think so.”

“Those are the best sorts of stories.”

“Do they tell them at your school?”

He shrugged. “Sometimes.”

“What’s a Click-clack the Rattlebag story?”

He was a precocious child, and was unimpressed by his sister’s boyfriend’s ignorance. You could see it on his face. “Everybody knows them.”

“I don’t,” I said, trying not to smile.

He looked at me as if he was trying to decide whether or not I was pulling his leg. He said, “I think maybe you should take me up to my bedroom, and then you can tell me a story before I go to sleep, but a very not-scary story because I’ll be up in my bedroom then, and it’s actually a bit dark up there, too.”

I said, “Shall I leave a note for your sister, telling her where we are?”

“You can. But you’ll hear when they get back. The front door is very slammy.”

We walked out of the warm and cosy kitchen into the hallway of the big house, where it was chilly and draughty and dark. I flicked the light-switch, but nothing happened.

“The bulb’s gone,” the boy said. “That always happens.”

Our eyes adjusted to the shadows. The moon was almost full, and blue-white moonlight shone in through the high windows on the staircase, down into the hall. “We’ll be all right,” I said.

“Yes,” said the boy, soberly. “I am very glad you’re here.” He seemed less precocious now. His hand found mine, and he held on to my fingers comfortably, trustingly, as if he’d known me all his life. I felt responsible and adult. I did not know if the feeling I had for his sister, who was my girlfriend, was love, not yet, but I liked that the child treated me as one of the family. I felt like his big brother, and I stood taller, and if there was something unsettling about the empty house I would not have admitted it for worlds.

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The stairs creaked beneath the threadbare stair-carpet.

“Click-clacks,” said the boy, “are the best monsters ever.”

“Are they from television?”

“I don’t think so. I don’t think any people know where they come from. Mostly they come from the dark.”

“Good place for a monster to come.”

“Yes.”

We walked along the upper corridor in the shadows, walking from patch of moonlight to patch of moonlight. It really was a big house. I wished I had a flashlight.

“They come from the dark,” said the boy, holding on to my hand. “I think probably they’re made of dark. And they come in when you don’t pay attention. That’s when they come in. And then they take you back to their… not nests. What’s a word that’s like nests, but not?”

“House?”

“No. It’s not a house.”

“Lair?”

He was silent. Then, “I think that’s the word, yes. Lair.” He squeezed my hand. He stopped talking.

“Right. So they take the people who don’t pay attention back to their lair. And what do they do then, your monsters? Do they suck all the blood out of you, like vampires?”

He snorted. “Vampires don’t suck all the blood out of you. They only drink a little bit. Just to keep them going, and, you know, flying around. Click-clacks are much scarier than vampires.”

“I’m not scared of vampires,” I told him.

“Me neither. I’m not scared of vampires either. Do you want to know what Click-clacks do? They drink you,” said the boy.

“Like a Coke?”

“Coke is very bad for you,” said the boy. “If you put a tooth in Coke, in the morning, it will be dissolved into nothing. That’s how bad coke is for you and why you must always clean your teeth, every night.”

I’d heard the Coke story as a boy, and had been told, as an adult, that it wasn’t true, but was certain that a lie which promoted dental hygiene was a good lie, and I let it pass.

“Click-clacks drink you,” said the boy. “First they bite you, and then you go all ishy inside, and all your meat and all your brains and everything except your bones and your skin turns into a wet, milk-shakey stuff and then the Click-clack sucks it out through the holes where your eyes used to be.”

“That’s disgusting,” I told him. “Did you make it up?”

We’d reached the last flight of stairs, all the way in to the big house.

“No.”

“I can’t believe you kids make up stuff like that.”

“You didn’t ask me about the rattlebag,” he said.

“Right. What’s the rattlebag?”

“Well,” he said, sagely, soberly, a small voice from the darkness beside me, “once you’re just bones and skin, they hang you up on a hook, and you rattle in the wind.”

“So what do these Click-clacks look like?” Even as I asked him, I wished I could take the question back, and leave it unasked. I thought: Huge spidery creatures. Like the one in the shower that morning. I’m afraid of spiders.

I was relieved when the boy said, “They look like what you aren’t expecting. What you aren’t paying attention to.”

We were climbing wooden steps now. I held on to the railing on my left, held his hand with my right, as he walked beside me. It smelled like dust and old wood, that high in the house. The boy’s tread was certain, though, even though the moonlight was scarce.

“Do you know what story you’re going to tell me, to put me to bed?” he asked. “It doesn’t actually have to be scary.”

“Not really.”

“Maybe you could tell me about this evening. Tell me what you did?”

“That won’t make much of a story for you. My girlfriend just moved in to a new place on the edge of town. She inherited it from an aunt or someone. It’s very big and very old. I’m going to spend my first night with her, tonight, so I’ve been waiting for an hour or so for her and her housemates to come back with the wine and an Indian takeaway.”

“See?” said the boy. There was that precocious amusement again. But all kids can be insufferable sometimes, when they think they know something you don’t. It’s probably good for them. “You know all that. But you don’t think. You just let your brain fill in the gaps.”

He pushed open the door to the attic room. It was perfectly dark, now, but the opening door disturbed the air, and I heard things rattle gently, like dry bones in thin bags, in the slight wind. Click. Clack. Click. Clack. Like that.

I would have pulled away, then, if I could, but small, firm fingers pulled me forward, unrelentingly, into the dark.

Neil Gaiman will be doing two events at the Hay Festival on 29 May. Trigger Warning: Short Fictions and Disturbances is published by Headline. To buy it for £16.99 from the Telegraph Bookshop, call 0844 8711514 or visit books.telegraph.co.uk