Sam Okafor was seven years old, and he had a monster under his bed.

He told me so on my very first Tuesday. I’d answered an ad on the board outside the uni library — reliable sitter wanted, Tuesday nights, nurse working nights, one boy, very sweet, slightly dramatic — and his mum, Grace, had hired me after a twenty-minute interview and a long, measuring look.

That night, as I tucked him in, Sam had grabbed my sleeve and said very seriously, “Don’t look under the bed, Ivy. Mothball doesn’t like strangers.”

“Mothball?”

“He’s my friend. He eats the bad dreams.” Sam had considered me with Grace’s exact measuring look. “He might like you. You look tired. Tired people have lots of bad dreams.”

I’d laughed. He wasn’t wrong.

That was four months ago. Since then I’d learnt a great deal about Mothball. He was very big, apparently. Not very old, for a monster. Sam said this was his first bed. He had long fingers and glowing eyes and smelled like the inside of a cupboard. He didn’t like the light, so the hall light had to stay off and the door had to stay open exactly a hand’s width. He liked it when Sam told him jokes. His favourite was the one about the cow with no legs.

Grace had told me, apologetically, that Mothball had turned up two years ago. Right after Sam’s dad left. Right around the time the nightmares started.

“The school counsellor says it’s healthy,” she’d said, rubbing her eyes in the kitchen at eleven at night in her scrubs. “A coping mechanism. He hasn’t had a single bad night since Mothball moved in.” She’d smiled wearily. “Just play along. Please.”

So I played along. I said goodnight to Mothball every Tuesday. I left the door open exactly a hand’s width. And I didn’t look under the bed.

I didn’t believe in him. Obviously. I was a twenty-six-year-old nursing student with a mortgage-sized student loan and a working understanding of the human brain. I knew exactly what imaginary friends were.

And I knew what nightmares were, too. I’d had them for years. Ever since a winter I tried very hard not to think about. They came three or four nights a week, and they always woke me up gasping in the dark, and I never, ever got back to sleep. So I understood why a frightened little boy would invent a monster to eat them. Some nights I’d have given anything for one of my own.

Then, on a Tuesday in late autumn, the power went out.

It was a little after ten. A storm had come in off the harbour, all wind and rain lashing at the windows, and Sam had been asleep for two hours. I was on the couch with my pharmacology notes, half-asleep myself, when the lamp flickered and died. The fridge stopped humming. The whole house went silent and black.

And Sam screamed.

I was off the couch before I knew it, banging my shin on the coffee table, fumbling for my phone torch with shaking fingers. His screams went on and on, high and terrified, the way children scream when they’re still half inside the dream. I ran down the dark hall with my heart in my throat.

His door was open a hand’s width. I shoved it wide.

And stopped.

Sam was sitting bolt upright in bed in the dark, sobbing. I could just make out his small shape against the faint grey of the window.

And beneath his bed, two eyes were shining.

They were huge. Pale gold, like a cat’s eyes in headlights, but far too big and far too high apart to belong to any cat. They glowed steady and calm in the black space between the bed frame and the floor.

Then something moved.

A hand slid out from under the bed. It was vast — longer than my forearm, grey-black and shadowy, with long, jointed fingers tipped in dark, curving claws. It moved slowly. Carefully. It reached up over the edge of the mattress and found the blanket Sam had kicked off in his thrashing.

And it drew the blanket back up over him, and tucked it in.

Sam’s sobs hitched. Slowed. The great clawed hand rested on the blanket over his chest, very lightly, the way you’d rest a hand on a sleeping puppy. A sound came from under the bed. Low and soft and rumbling. Almost too deep to hear.

It was humming.

Sam’s breathing evened out. His small body slumped back against his pillow. Within a minute, he was asleep.

The hand stayed where it was a moment longer. Then it withdrew, slowly, sliding back into the dark under the bed.

The golden eyes turned towards the door.

Towards me.

My phone was still in my hand. I’d never switched the torch on. I stood frozen in the doorway with my thumb over the button and my heart hammering so hard I could hear it.

The eyes regarded me for a long, long moment.

Then a voice came out of the dark. Low and rough and very quiet, so quiet it wouldn’t wake the boy. It sounded like gravel shifting at the bottom of a well.

“Please,” it said. “Don’t turn on the light.”

I didn’t turn on the light.

I don’t know how long I stood there. Long enough for the rain to ease off against the window. Long enough for my legs to start shaking. Long enough for Sam to roll over in his sleep, mumble something about a cow, and start to snore.

Then I backed out into the hallway and slid down the wall until I was sitting on the carpet, just outside his door. Open a hand’s width.

I put my phone face-down on the floor beside me.

“Mothball,” I said, very quietly. My voice wobbled. “I presume.”

A pause. Then that low, gravel-deep voice drifted out through the gap in the door.

“He named me after the smell,” it said. “The first night. I’m told I smell like the inside of a cupboard.”

I let out a laugh. It came out high and cracked and slightly hysterical. I clapped a hand over my mouth.

“You’re real,” I whispered.

“I’m afraid so.”

“You’re actually real.”

“Yes.” A pause. “I was hoping you’d never find out. You seemed very sensible.”

I sat on the hall carpet in the dark and tried to think. I was a sensible person. I was nearly a nurse. I had a working understanding of the human brain. And there was a monster under Sam Okafor’s bed, and he had just tucked the blanket back over a sobbing seven-year-old more tenderly than I’d ever seen anyone do anything.

“What are you?” I asked.

“Young,” he said, a little defensively. “For my kind. Old enough to leave the deep dark and find a bed of my own. This is my first.” A pause. “We live in the dark places under things. Beds, mostly. We eat what grows there in the night.”

“Nightmares.”

“Nightmares.” His voice softened. “The boy had very bad ones, when I found him. His father had just gone. He was dreaming every night of doors closing. I could smell it from three streets away.”

Something tightened in my chest.

“So you just… moved in.”

“It was my first night out of the deep. I was starving, and I had no idea what I was doing, and he was so frightened.” A low, rumbling sound, almost a sigh. “Most of us move on after a season. Find a new bed. But then he told me a joke about a cow with no legs, and I found I didn’t want to leave.”

I pressed the back of my hand against my mouth. My eyes were stinging.

“Ground beef,” I said, muffled.

A pause. Then a sound came from under the bed, so deep I felt it through the floor. It took me a moment to realise it was laughter.

“Ground beef,” Mothball agreed. “He tells it every night. He has not once got tired of it.”

We sat there in the dark for a long time after that. Him under the bed, me in the hallway. The rain softened to a drizzle. The storm moved off over the harbour. He told me about Sam — his favourite dinosaur, the boy at school who’d pushed him, the way he still left a biscuit under the bed for Mothball every Friday. I told him about Grace’s double shifts, and my placement at the hospital, and the patient who’d thrown a bedpan at me that afternoon.

He was funny. That was the strangest part. Dry and a little awkward and wryly, quietly funny, in that low gravel voice, like someone who’d learnt to talk mostly from a seven-year-old and a great deal of late-night television through the wall.

When the power finally flickered back on, I heard him shift, fast, deeper into the dark under the bed.

“The hall light,” he said quickly. “Please.”

I reached up and switched it off before it could spill through the door.

“Why?” I asked. “What happens if the light touches you?”

He was silent for a long moment.

“We’re not meant to be seen,” he said at last. “Not all of us. Not in the light. That’s the oldest rule there is. They drilled it into us before they ever let us out of the deep.” A pause. “I’ve never actually tested it.”

I didn’t push. I heard Grace’s key in the front door ten minutes later, and I scrambled to my feet and smoothed down my hair and went to tell her about the storm.

But before I went, I crouched by the gap in Sam’s door one last time.

“Goodnight, Mothball,” I whispered.

The golden eyes opened in the dark beneath the bed. Watching me.

“Vesper,” he said quietly. “My name. My real one. Since you’re not imaginary either.”

“Vesper,” I repeated.

The eyes narrowed, very slightly, the way eyes narrow when someone smiles.

“Goodnight, Ivy,” he said. And then, just as I was rising to leave: “You should try to sleep tonight. Your nightmares smell very loud.”