Coraline sat down on the sofa and ate her apple.

"Please," said her other mother. "Don't be difficult." She walked into the drawing room and clapped her hands twice. There was a rustling noise and a black rat appeared. It stared up at her. "Bring me the key," she said.

The rat chittered, then it ran through the open door that led back to Coraline's own flat.

The rat returned, dragging the key behind it.

"Why don't you have your own key on this side?" asked Coraline.

"There is only one key. Only one door," said the other father.

"Hush," said the other mother. "You must not bother our darling Coraline's head with such trivialities." She put the key in the keyhole and twisted. The lock was stiff, but it clunked closed.

She dropped the key into her apron pocket.

Outside, the sky had begun to lighten to a luminous grey.

"If we aren't going to have a midnight snack," said the other mother, "we still need our beauty sleep. I am going back to bed, Coraline. I would strongly suggest that you do the same."

She placed her long white fingers on the shoulders of the other father, and she walked him out of the room.

Coraline walked over to the door at the far corner of the drawing room. She tugged on it, but it was tightly locked. The door of her other parents' bedroom was now closed.

She was indeed tired, but she did not want to sleep in the bedroom. She did not want to sleep under the same roof as her other mother.

The front door was not locked. Coraline walked out into the dawn and down the stone steps. She sat down on the bottom step. It was cold.

Something furry pushed itself against her side in one smooth, insinuating motion. Coraline jumped, then breathed a sigh of relief when she saw what it was.

"Oh. It's you," she said to the black cat.

"See?" said the cat. "It wasn't so hard recognising me, was it? Even without names."

"Well, what if I wanted to call you?"

The cat wrinkled its nose and managed to look unimpressed. "Calling cats," it confided, "tends to be a rather overrated activity. Might as well call a whirlwind."

"What if it was dinnertime?" asked Coraline. "Wouldn't you want to be called then?"

"Of course," said the cat. "But a simple cry of 'dinner!' would do nicely. See? No need for names."

"Why does she want me?" Coraline asked the cat. "Why does she want me to stay here with her?"

"She wants something to love, I think," said the cat. "Something that isn't her. She might want something to eat as well. It's hard to tell with creatures like that."

"Do you have any advice?" asked Coraline. The cat looked as if it were about to say something else sarcastic. Then it flicked its whiskers, and said, "Challenge her. There's no guarantee she'll play fair, but her kind of thing loves games and challenges."

"What kind of thing is that?" asked Coraline. But the cat made no answer, simply stretched, luxuriantly, and walked away. Then it stopped, and turned, and said, "I'd go inside if I were you. Get some sleep. You have a long day ahead of you."

And then the cat was gone. Still, Coraline realised, it had a point. She crept back into the silent house, past the closed bedroom door beyond which the other mother and the other father… What? she wondered. Slept? Waited? And then it came to her that, should she open the bedroom door, she would find it empty, or, more precisely, that it was an empty room and it would remain empty until the exact moment that she opened the door.

Somehow, that made it easier. Coraline walked into the green and pink parody of her own bedroom. She closed the door and hauled the toybox in front of it-it would not keep anyone out, but the noise somebody would make trying to dislodge it would wake her, she hoped.

The toys in the toybox were still mostly asleep, and they stirred and muttered as she moved their box, and then they went back to sleep. Coraline checked under her bed, looking for rats, but there was nothing there. She took off her dressing gown and slippers and climbed into bed and fell asleep with barely enough time to reflect, as she did so, on what the cat could have meant by a challenge.

Coraline was woken by the mid-morning sun, full on her face.

For a moment she felt utterly dislocated. She did not know where she was; she was not entirely sure who she was. It is astonishing just how much of what we are can be tied to the beds we wake up in in the morning, and it is astonishing how fragile that can be.

Sometimes Coraline would forget who she was while she was daydreaming that she was exploring the Arctic, or the Amazon rainforest, or darkest Africa, and it was not until someone tapped her on the shoulder or said her name that Coraline would come back from a million miles away with a start, and all in a fraction of a second have to remember who she was, and what her name was, and that she was even there at all.

Now there was sun on her face, and she was Coraline Jones. Yes. And then the green and pinkness of the room she was in, and the rustling of a large painted paper butterfly as it fluttered and beat its way about the ceiling, told her where she had woken up.

She climbed out of the bed. She could not wear her pyjamas, dressing gown and slippers during the day, she decided, even if it meant wearing the other Coraline's clothes. (Was there an other Coraline? No, she decided, there wasn't. There was just her.) There were no proper clothes in the cupboard, though. They were more like dressing-up clothes or (she thought) the kind of clothes she would love to have hanging in her own wardrobe at home: there was a raggedy witch costume; a patched scarecrow costume; a future-warrior costume with little digital lights on it that glittered and blinked; a slinky evening dress all covered in feathers and mirrors. Finally, in a drawer, she found a pair of black jeans that seemed to be made of velvet night, and a grey sweater the colour of thick smoke with faint and tiny stars in the fabric which twinkled.

She pulled on the jeans and the sweater. Then she put on a pair of bright-orange boots she found at the bottom of the cupboard.

She took her last apple out of the pocket of her dressing gown, and then, from the same pocket, the stone with the hole in it.

She put the stone into the pocket of her jeans, and it was as if her head had cleared a little. As if she had come out of some sort of a fog.

She went into the kitchen, but it was deserted.

Still, she was sure that there was someone in the flat. She walked down the hall until she reached her father's study, and discovered that it was occupied.

"Where's the other mother?" she asked the other father. He was sitting in the study, at a desk which looked just like her father's, but he was not doing anything at all, not even reading gardening catalogues as her own father did when he was only pretending to be working.

"Out," he told her. "Fixing the doors. There are some vermin problems." He seemed pleased to have somebody to talk to.

"The rats, you mean?"

"No, the rats are our friends. This is the other kind, big black fellow, with his tail high."

"The cat, you mean?"

"That's the one," said her other father.

He looked less like her true father today. There was something slightly vague about his face-like bread dough that had begun to rise, smoothing out the bumps and cracks and depressions.

"Really, I mustn't talk to you when she's not here," he said. "But don't you worry. She won't be gone often. I shall demonstrate our tender hospitality to you, such that you will not even think about ever going back." He closed his mouth and folded his hands in his lap.

"So what am I to do now?" asked Coraline. The other father pointed to his lips. Silence. "If you won't even talk to me," said Coraline, "I am going exploring."