When she got up to the next level she found Monkey-Boy looking at the human exhibits: models of cavemen and Neanderthals and old skeletons were all mixed up with stuffed apes. Ella didn’t like the models. They were too realistic. They had clever, sneaky eyes and she feared they’d come alive. Monkey-Boy was making faces at one of them.

‘I can climb higher than any of these losers,’ he said.

‘That’s because they’re dead,’ said Ella. ‘Dead and stuffed. They’re creepy.’

‘The dead can’t hurt us,’ said Monkey-Boy.

Ella looked at the figures standing there, waiting forever. The orange hairy face of an orang-utan, the friendly face of a chimp, the glass eyes of a caveman, and a pale face, with dark-rimmed eyes, white skin, black hair, at the back, behind the other exhibits, in the darkness.

That blinked.

Ella opened her mouth, wanting to scream, but could make no sound come out. Her breath was tangled inside her. Frozen.

She grabbed Monkey-Boy’s arm. So tight he yelped and pulled away sharply.

‘Be careful,’ he said, and then he saw her face. Panic came into his eyes. He searched around wildly, trying to see what it was that had spooked her. Finally Ella pointed, waving her arm … at nothing. Only shadows.

The face had gone.

She had seen it, though. She was sure she had seen it. Something alive. The slenderman. The spider. The thing. There was movement to their right, coming fast round the end of the cabinets, and finally she screamed, long and high and shrill, and Monkey-Boy saw it too. A person. A boy. Tall. Dressed all in black, his clothes shiny and filthy, with dark stains all over, and in his hands a knife, raised and ready.

Again Ella screamed. And she ran and Monkey-Boy ran and the black figure ran after them. And Ella got trapped among the cabinets. Could go no further. Monkey-Boy with her. Trembling. There had to be a way out, but in her panicked confusion the cabinets had made a wall around her, the apes and cavemen grinning at her.

And then she heard voices. People were coming out of the minerals gallery at the far end of the balcony, behind the slenderman.

‘What is it? What’s the matter?’ It was Maeve, running ahead of the others, unarmed but unafraid.

‘What is it?’ she repeated. The only answer Ella could give was another scream.

The slenderman made a grab for Monkey-Boy, who somehow managed to duck and wriggle away from him. He slashed at thin air with his bright and shiny knife, but Monkey-Boy jumped up on to the stone railing, then swung out and round and up on to one of the stone columns that supported the great arches above them. He scampered up, got clear and disappeared from sight.

That left only Ella. She crouched down, trying to make herself small.

At last Maeve had realized what was going on.