“Mum! Ben won’t get out of my room. He’s messing up all my stuff,” Kate yelled round the door of her bedroom, holding on to a squalling Ben by a handful of sweatshirt. “Ouch! Mum, he’s kicking me.”

Ruth emerged from the study just as Ben dissolved into theatrical sobs and Kate let go. “Come on, Ben. I thought you wanted to make biscuits. Leave Kate alone, she’s trying to pack.”

The sobbing stopped abruptly. “Is she going away? Can I have her room?”

“I’m only going away for one night, idiot. I already told you about it.”

“Don’t call him an idiot,” said Ruth mildly. “It’s only half true. Come on, Ben.”

Kate shut the bedroom door. Why was it always so hard to get any peace or privacy in this house? Sometimes it felt as though she lived with about twenty people, not just three.

She found herself envying David and his dad and then felt awful that she’d done so. She knew how lonely both of them had been since his mum died. Neither of them said so any more, but she could see it in their eyes sometimes when they were round here and didn’t know she was paying attention: a longing as they watched Mum and Ben.

She checked her bag once more, then went to see if there were any bits of biscuit dough that needed eating.

“Here they are,” she called from the window where she’d been keeping watch for the last ten minutes.

“A kiss, a kiss,” yelled Ben, suddenly agitated in case Kate disappeared without saying goodbye.

Mum and Dad, to her relief, didn’t make a fuss over her going, just a quick kiss each and a reminder to thank Alastair for taking them.

At the museum, they found a parking space just across from the main entrance and joined the trickle of people carrying sleeping bags and backpacks.

“I have to come and sign you in and leave emergency numbers,” said Alastair, “but don’t worry, I’ll push off as fast as possible. I don’t want to spoil your fun.”

Inside the Main Hall it was darker than they had expected, only a few lights shining, the brightly lit Information Desk like a beacon, and as they went in the last few notes of the clock’s performance were dying away as it settled into quiet for the night.

Once Alastair had filled in a form signing them over officially, he gave David a quick hug and strode off to the door without looking back.

“Dump your stuff over there with the rest just now and have a seat,” said the tall, dark-haired man at the desk. “There’s another three to come and then we can get started,” he added.

Kate read his name tag:

“Can we sleep anywhere?” she asked.

He laughed. “No. We don’t let you near the mummies, if that’s what you’re about to ask. We don’t want you scaring each other to death during the night. You can sleep here in the Main Hall, or in with the elephants or the British mammals or the fish. Fish or mammals are comfiest because there’s carpet on the floors.”

“All right, Sandy?” he asked a smaller, balding man who’d joined him at the desk as he was speaking.

“Aye, Gordon. Fine.”

“I’m away to sort the clock for the night. There’s still three to come,” said G for Gordon and set off up the hall with a big torch in one hand.

Kate and David sat down on one of the padded benches by the fish pool, eyeing the others already waiting there.

“Twenty-one,” said David.

“What?”

“People. And three to come makes twenty-four. Should be plenty of room, even if everyone decides to sleep in the same place.”

Three girls appeared up the steps from the front door, carrying rucksacks that made it look as though they’d come to stay for a week, accompanied by someone’s anxious-looking mum. She went through the form-filling, then an elaborately affectionate goodbye that left one of the girls scarlet with embarrassment.

“Okay,” said Gordon. “Good evening everyone and welcome to the museum sleepover. Anyone been on one before?”

A couple of boys raised their arms.

“You can just doze through the talk then, lads. It’ll be the same as you heard last time.”

He went on to explain where they could sleep, what they could and couldn’t do and so on. “Right. You’ve got ten minutes to go and reserve your spot for the night then back here for the VIP tour. Bring your torches.”

There was a scrum as everyone rushed for their belongings and groups separated off to each of the sleeping areas. Kate and David had decided on the British mammal hall and they made a little campsite by the seals; friendly faces, David thought, if they woke in the middle of the night.

Apart from them another two pairs were settling themselves in the room, one beside the dolphins, the other by the white cattle.

Back at the desk, Gordon and Sandy were counting heads. When a trio of boys appeared from the direction of the fish gallery, Sandy gave Gordon a nod and led them through a pair of tall wooden doors that said “Staff Only” and into the working heart of the museum, where animals went for taxidermy, fabric for conservation and pottery to be dated; a brief glimpse of each so that no one got bored. Round a corner they came to a table covered with cans of juice, pizza and chocolate biscuits, and for ten minutes they sat on the floor or leaned against the wall, happily pigging out.

“Well,” said Gordon, “are you ready for the spooky bit?” There was a chorus of affirmation. “Torches on then. This is when the lights go out.”

As he said it, the lights did go out and there were a few squeaks of mock alarm.

“Nobody gets scared too easy, do they?” asked Sandy.

“Nah.”

“Not likely.”

“Course not.”

“Switch on your torches then,” he continued. “Everyone ready?”

They filed out into the new, dark museum, Gordon leading and Sandy making sure no one got left behind, whether by accident or on purpose.

It was a moment before Kate realised they were in the Main Hall again. The yellow beams of light from the torches didn’t penetrate very far, but there was a half moon sailing high above the glass roof, giving just enough light to show faint outlines of the fish pools and the clock.

Gordon led them up the steps to the first floor and into the costume gallery, where blank-faced figures watched them from the display cases. It was quite spooky, Kate had to admit, especially when she noticed one figure in a yellow dress and hat, craning forward as though for a better look at them. No one talked above a whisper now, apart from a few slightly nervous laughs.

From there, they went to what everyone assumed would be the creepiest bit: the Egyptian section with its bound mummies and painted sarcophagi. For Kate it was a bit of a disappointment. If you were on your own in the dark it would be really scary, but with twenty-five other people so close it didn’t seem much different from how it was during the day, just darker.

Someone’s torch picked out a mummy with gold feet and a gold mask where his face would have been. He had huge ears and a daft smile that made him look like a cartoon character. Kate pointed him out to David and they were overcome with a fit of the giggles.

Last, they went to the dinosaurs. The skeletons looked bigger than they did in daylight, especially the Ichthyosaur, hanging above them as though still swimming.

“You can have a wander round here for five minutes. Down or up one level’s all right but don’t go out of this section on your own.”

People spread out slowly. Kate and David joined the group that headed upstairs. There were big skeletons up here too: giant sloth, armadillo and elk, magnified by torchlight, but there were much smaller things also: beautiful Eskimo carvings of bone and walrus ivory. Kate’s favourite was an otter lying on its back and she moved away from the others to look at it now. It looked so funny, with its hind legs curled up and its front paws at the sides of its head as though it had just heard bad news.

As she looked at it, she had a sudden sensation that someone was standing just behind her. She turned, expecting to see David, but her eye was caught by the reflection, in a display case, of something moving, low and fast. She swung round with a gasp.

“David, did you see …?”

Her voice died away. There was no one there. She could make out David, with some of the others, at the other side of the gallery. She swung the torch from side to side, the hair rising on the back of her neck.

She forced herself to walk slowly over to the group, heart thumping in her chest as she tried to calm herself and pretended to listen to their discussion. It was no good: the feeling that someone else was there wouldn’t go away.

“Kate?”

She jumped slightly when David spoke.

“Are you okay?”

“Can we go back down now? Its cold up here,” she lied as she shivered.

She was going to tell David about the feeling, but it went as soon as she started down the stairs, so suddenly that it stopped her in her tracks for a couple of seconds.

Fool. Scaring yourself over nothing.

She could almost believe it was true.