He went out to the garage at the back of the house to sit in his dad’s car.

The 1961 Aston Martin DB4 Coupe was his dad’s pride and joy, and Samuel had been for only a handful of trips in it before his dad left, and even then his dad had seemed to resent Samuel’s presence slightly, like a child forced to allow another child to play with his favorite toy. Because his dad was living in an apartment in the north, with no garage, he had decided to leave the car in Biddlecombe for now. In a way Samuel was pleased, because he believed that meant his dad might return home at some point. If he took the car away permanently, though, there would be nothing of him left. It would be a sign, thought Samuel, a sign that the marriage was over and it was now just Samuel and his mum.

When Mrs. Johnson rose, they ordered in pizza, but his mum couldn’t finish hers and went back to bed. Every time she tried to recall what had happened at the supermarket her head began to hurt, and intermingled smells came to her, perfume and something rotten and bad that the scent would be able to hide for only so long.

That night, Mrs. Johnson had bad dreams, but they were only dreams.

Samuel Johnson’s nightmares, on the other hand, came alive.

SAMUEL WOKE TO FIND there was a monster under his bed. He didn’t just think there was a monster under there, the way very small boys and girls sometimes do; Samuel was no longer a very small boy and had accustomed himself to believe that, in all probability, monsters did not inhabit the spaces under beds. They particularly did not occupy the space under Samuel’s bed because there wasn’t any, every spare inch being taken up by games, shoes, candy wrappers, unfinished model aircraft, and a large box of toy soldiers with which Samuel no longer played but which he was most reluctant to get rid of, just in case.

Now all those objects were scattered across his bedroom floor, and a sound was coming from beneath his bed that resembled pieces of jelly being tossed from hand to hand by a troupe of tiny jugglers. In addition, Boswell was standing on the bed, trembling and growling.

Samuel felt a sneeze coming on. He tried every trick he knew to stop it. He held his nose. He took deep breaths. He pressed the tip of his tongue against the top row of his teeth, the way that Japanese samurai used to do when they didn’t want to reveal their presence to an enemy, all to no avail.

Samuel sneezed. It sounded like a rocket taking off. Instantly, all noise and movement from below his bed ceased.

Samuel held his breath and listened. He had the uncomfortable sense that a very squishy creature was also holding its breath, if it had any to hold. Even if it didn’t, it was definitely listening.

Maybe I imagined it, thought Samuel, even though he knew that he hadn’t. You didn’t imagine something squishing under your bed. Either it squished, or it didn’t, and something had definitely squished.

He looked around, and saw one of his socks lying at the end of his bed. As an experiment he leaned down to pick up the sock, then dangled it over the edge of the mattress before dropping it on the floor.

A long pink thing that might have been a tongue, or an arm, or even a leg, grabbed the sock and pulled it under the bed. Samuel heard chewing, and then the sock was spat out and a voice said, “Ewwwww!”

“Hello?” said Samuel.

There was no reply.

“I know you’re under there.”

Still no reply.

“Look, this is silly,” said Samuel. “I’m not getting off this bed. You can stay there for as long as you like. It’s just not going to happen.”

He counted to five in his head before he heard a sigh from beneath the mattress.

“How did you know?” said a voice.

“I heard you squish.”

“Oh. I’m new at this. Still getting the hang of it. You tricked me with that sock thing. Very clever, that. Tasted horrible. You need to get something done about your feet, by the way. They must stink something awful.”

“It’s a gym sock. I think it’s been there for a while.”

“Well, I suppose that explains it, but still. You could knock someone dead with a sock like that. Lethal weapon, that sock. It’s made me feel quite ill.”

“Serves you right,” said Samuel. “You shouldn’t be hanging around under people’s beds.”

“Well, it’s a job, innit?”

“Not much of a job.”

“Agreed, but you try being a demon of no set form in this day and age. It’s not like I’m going to get work looking after puppies, or singing babies to sleep. Frankly, it’s this or nothing.”

“What do you mean, ‘no set form’?”

The demon cleared its throat. “Technically, I’m a free-roaming ectoplasmic entity…”

“Which is?” asked Samuel, a little impatiently.

“Which is,” said the demon huffily, “if you’ll wait for me to finish, a demon capable of assuming almost any shape or form, based on psychic vibrations given off by its victim.”

“You’ve lost me,” said Samuel.

“Oh look, it’s not that complicated. I’m supposed to become whatever scares you. I just picked the whole slushy tentacled thing because, well, it’s a classic, isn’t it?”

“Is it?” asked Samuel. “So you’re a bit like an octopus, then?”

“A bit, I suppose,” admitted the demon.

“I quite like octopi.”

“Octopodes,” corrected the demon. “Don’t they teach you anything at school?”

“There’s no need to be rude,” said Samuel.

“I’m a demon. What do you expect me to be? Pleasant? Tuck you in and read you a story? You’re not very bright, are you?”

“No, you’re not very bright, turning up here in the dead of night and being caught out by an old sock. And you haven’t assumed a form that scares me. You’re an octopus.”

“I’m like an octopus,” said the demon. “But scarier. I think. It’s hard to see under here.”

“Whatever,” said Samuel. “If it’s all about psychic vibrations, then why didn’t you take the form of something else?”

The demon muttered something.

“I beg your pardon,” said Samuel. “I didn’t quite catch that.”

“I said, ‘I can’t do psychic vibrations.’” The demon sounded embarrassed.

“Why not?”

“They’re hard, that’s why not. You try it, see how much luck you have.”

“So you just take a form and hope that it will be scary? That all sounds a bit casual, to be honest.”

“Look, it’s my first time,” said the demon. “Are you happy now? It’s. My. First. Time. And I have to say that you’re being very hurtful. You’re not making this easy, you know.”

“I’m not supposed to make it easy,” said Samuel. “What would be the point in that?”

“Just saying, that’s all,” said the demon. Samuel heard it sniff dismissively.

“Okay,” said Samuel. “I’m not very keen on spiders.”

“Really?” said the demon.

“Yes.”

“You’re not just saying?”

“No, I really don’t like them very much at all. Why don’t you start with that and see how you get along?”

“Oh, I will. Thanks very much. Very nice of you. Give me a minute, will you?”

“Take your time.”

“Right you are. Much appreciated. Don’t go anywhere, now.”

“Wouldn’t dream of it,” said Samuel.

He sat on the bed, humming to himself and patting Boswell. From under the mattress came various squelching sounds, and the occasional grunt of effort. Finally, there was silence.

“Er, a question,” said the demon.

“Yes?”

“Do spiders have ears?”

“Ears?”

“You know, huge big flappy things.”

“No. They feel vibrations with the hairs on their legs.”

“All right, all right, I didn’t ask for a lecture. It was just a simple question.”

There was silence again.

“What are the things with big flappy ears, then?” said the demon.

Samuel thought about the question. “Elephants?” he suggested.