"I said it was destroyed because the people thought it was evil," the professor corrected him. "They were mistaken. They gave it a name, Raven's Gate, because the raven has always been a.s.sociated with death. They had a memory that connected the stones with something horrible... But after all the years that had pa.s.sed, they had forgotten what it was. And in the end they came to think that it was the stones themselves that were evil. So they tore them down."

"So the gate was destroyed!" Matt exclaimed.

Professor Dravid shook his head. "The stones were destroyed, not the gate," he said. "How can I explain it to you? It's like an idea. If you write something down on a sheet of paper and then burn the paper, do you burn the idea? Of course not! The stones are gone, but the gate is still in place."

Richard sighed. "Let me get this straight, Professor," he said. "A very long time ago, the world was ruled by evil creatures called the Old Ones. However, five kids appeared and threw them out. These kids then built a barrier, which came to be known as Raven's Gate. Unfortunately the stones that marked the gate were knocked down by medieval peasants who didn't know any better. But it doesn't matter that much because the gate is still there after all. Is that about it?"

"Your sarcasm does you no credit, Mr Cole," Dravid replied. "But you have summed up what I said more or less accurately."

"Miss Ashwood knew about this?" Matt said.

"Yes. As I explained to you, we share our knowledge. We have sworn not to reveal it. That's why she couldn't tell you anything when you met."

"But you've told us," Matt went on. "You said that the main reason for the Nexus was to help me with something I have got to do. But I'm still not clear what that is a or what any of this has got to do with me."

"I think you know."

"No!" Matt looked him in the eye. "You're wrong."

"Then you must meet the Nexus. The other members are on their way back to London. They'll be here tomorrow night. I'll look after you until then."

"Forget it," Richard said. "We've got day-return tickets. We're going back to York this evening."

"That's the last thing you must do. It's vital you don't go anywhere near Lesser Malling." He turned again to Matt. "I don't want to frighten you any more than you have been already, but I believe you are in terrible danger."

"Why?"

"I've told you why Raven's Gate was built. It was a barrier between two worlds and it was closed and locked. But for many centuries there have been people who have been trying to open it again. Of course, they haven't found it easy. They've had to develop special knowledge ... special powers."

"You mean magic," Matt said.

"We are just two days away from the start of Roodmas," Dravid said. "It begins at sunset on the thirtieth of April. It is one of the most important days in the witches' calendar. A day when dark powers are at their strongest. When black sabbath is celebrated and evil has its way."

"Mrs Deverill..." Matt began.

"I have absolutely no doubt that she and the other villagers of Lesser Malling are involved in some sort of black magic. Of course you will sneer, Mr Cole. But black magic is still practised today all over the world. Yorkshire has a long history of witchcraft a and although the witches of medieval times are gone, their descendants live on.

"A black sabbath on Roodmas will require three ingredients, the same as you will find in any such ceremony. The first is ritual. Matt has already described the whispers that he heard. The second is fire. You saw the dogs rise out of the flames. But the third, of course, is blood. They must have a sacrifice, and the best sacrifice of all would be that of a child..."

Matt stood up. All the colour had drained from his face. "They brought me there to kill me," he said.

"I'm afraid so."

"We should go to the police!" Richard exclaimed. "You're talking about a bunch of lunatics, and the whole lot of them ought to be locked up..."

"Matt has already been to the police," Dravid reminded him. "Two of them ignored him. The one who didn't, died."

"Why me?" Matt asked. "Why did they choose me? Why couldn't it be someone else?"

"I think you know the answer to that," Dravid said quietly. He stopped and laid a hand gently on Matt's shoulder. "I'm sorry. I know how hard it must be for you to accept all this. But you'll have time. I'll put you in a hotel tonight. The Nexus will take care of the cost. And from now on, we'll look after you."

"Why? What do you want from me?"

"We just want you to be safe."

"I wish it wasn't so cold," Matt said.

The three of them left the study. They went along the corridor past a row of gla.s.s cases. Wax figurines of primitive people stared out at them. The sound of their footsteps echoed against the ceiling, flapping about the air like invisible birds. Halfway down the main staircase, Dravid stopped. "The keys!" he said. "They're in my jacket! I'll need them to let us out."

Hastily he stumbled back up the staircase and along the corridor. Matt watched him. It was only now that he realized how vast the museum was. Professor Dravid was just a tiny figure, crossing a balcony high above them. They saw the door of the study open and the light go on.

"Listen, Matt," Richard said. "This is all just a bad dream. Nothing can happen to you."

Matt stepped back from him. "You still don't believe it!" he exclaimed.

"Yeah a sure I believe in it. Old Ones and gates and witches and blood sacrifice! Look around you, for heaven's sake! There are rockets going to Mars. We've got satellites beaming phone conversations all around the world. They've unlocked the genetic code. And you've still got throwbacks like Dravid going on about devils and demons. Well take it from me, Matt. These five kids saving the world with magical powers don't exist."

"Of course they exist," Matt said. And suddenly he knew. It was very simple. "I'm one of them."

There was a sound. Something invisible had been thrown a or had flown a through the air. Matt and Richard heard someone cry out and looked back at the stairs. Sanjay Dravid had appeared again. He was walking slowly, his footsteps uneven, as if he was drunk or drugged. His hand was clasped to his neck. He stopped and let his hand fall and, with a gasp of horror, Matt saw a terrible wound a a gaping, horizontal line, perhaps cut with a sword a across the professor's neck. Blood curtained down, soaking into his jacket and shirt. Dravid raised his hands feebly. He tried to speak. Then he toppled forward on to his face and lay still.

Richard swore. Matt tore his eyes away from the motionless figure and looked at the main doors on the other side of the gallery. It was colder than ever. Even without seeing it, he knew there was danger all around.

And the doors were locked.

BONES.

For what seemed like an eternity Richard and Matt stood where they were, staring at the still figure lying at the top of the stairs. Blood was spreading around Dravid's head. But there was no sign of an attacker. The museum was as empty and silent as it had been when they first came in. And there was something else. The air was icy and seemed to have thickened. It had a white, smoky quality, like a bad photograph.

Richard was the first to recover. "Wait here!" he said, then bounded forward towards the stairs.

"Where are you going?" Matt called after him.

"The keys!"

He took the steps two at a time, not wanting to get any closer to Dravid but knowing there was no other way. The blood had reached the edge of the first step and was already trickling down. Richard knelt down beside the body, trying not to look at the horrible wound. Then suddenly Dravid opened his eyes. Miraculously he was still alive.

"Five..." The single word was all he could manage.

"Don't say anything. I'll get help." Richard didn't know what else to say. He was lying. The professor was far beyond help.

Dravid extended a trembling hand, which clasped a ring of keys. Richard took them gently. For a moment the two of them looked into each other's eyes. Dravid tried to speak again but it was too much for him. He coughed painfully. Then his head fell back and his eyes closed.

Holding the keys, Richard stood up. He could see Matt below him, some distance away, and knew what he was thinking. Right now there was a killer inside the museum. Someone a or something a had attacked Professor Dravid and they would surely be next. But what were they up against? Why couldn't they see anything? Moving slowly now, Richard went back down the stairs, his every sense alert. The two of them were so small in this enormous place. He felt horribly exposed.

"Did you get them?" Matt asked.

"Yes." Richard held up the keys. "Let's get out of here."

"What about Professor Dravid?"

"He's dead. I'm sorry. There's nothing we can do."

"But what killed him?"

"I don't know." Richard gazed upwards, his eyes sweeping across the vaulted ceiling. "But let's not stay to find out."

He turned and at that moment there was a sudden whirl in the air. Matt threw a protective arm across his face and staggered into Richard.

"What's wrong?" Richard demanded.

"There was something..." Matt looked around him but there was nothing there. "Something flew near my head," he insisted.

"Flew?"

"Yes."

"Did you see what it was?"

"No. But I sensed it. It came so close... I felt it go past."

"I can't see anything."

But then it dived towards them again, sweeping down out of the mist, and this time there could be no mistaking it, even if it took Matt precious seconds to work it out. Triangular and white, the creature was neither living nor dead, coming at them like something out of a hideous dream. It had eye sockets but no eyes, wings but no feathers, a bulging ribcage with nothing inside. Moving faster than ever, almost a blur, it shot down. Its claws were stretched out and its needle-sharp teeth were bared in an evil grimace. Matt fell back. He felt one of the wings shudder past his face and knew that if he had waited a second longer he would have been decapitated. Now he understood what had happened to Professor Dravid.

Richard reached down and helped him up. "Did you see it?" he muttered.

"Of course I did."

"You saw what it was?"

"Yes!"

"What?"

"I don't know." Matt had recognized it but he couldn't put it into words.

"It's a trick," Richard said. "It has to be a trick. It wasn't real."

They had been attacked by something that couldn't fly, that couldn't even exist. It was a creature that hadn't been seen on the planet for many millions of years. A pterodactyl. Except that it wasn't quite a pterodactyl. It was the fossilized skeleton of a pterodactyl, wired together and put on display at the Natural History Museum. It had been brought to life and now it was somewhere above them.

"Look out!"

Matt shouted the warning as the pterodactyl swooped down a third time, plummeting out of the gloomy heights of the hall and hurtling towards them. He had no doubt that the claws would rip his flesh away if he allowed them to make contact. The creature was as vicious as it had been when it had flown over the prehistoric world. It was being guided, being used as an impossible weapon. Its head and claws missed Matt by centimetres and he thought he had escaped. But as it went past, one of its wing tips brushed his face and he felt a searing pain as the bone cut into him. He gasped and put a hand to his cheek. There was blood on his palm. The pterodactyl performed an aerial somersault and soared back the way it had come. There had been no noise, no warning. Nothing. The museum was utterly silent.

"Matt..." Richard began. There was panic in his eyes.

"I'm OK," Matt said, his hand still pressed against his cheek.

"You've been cut."

"I don't think it's deep."

Richard craned his neck, staring up at the ceiling. "We've got to go."

Matt grimaced. "I wasn't thinking of staying."

He had barely spoken the words before the pterodactyl was back. This time Richard was the target. The outstretched wing slashed through the air. It was as sharp as a sword. Richard cursed.

"Richard..." For a dreadful moment Matt thought he'd been hit.

"It's OK. It missed me. It's gone."

"Yes. But what about the others?"

"What...?"

Professor Dravid had called it the most remarkable exhibition of dinosaur fossils ever seen in London. The pterodactyl was only one of them. There were dozens more all around them. Richard and Matt were standing in the middle of an X-ray version of Jura.s.sic Park.

Even as Richard realized the true nature of the danger, there was an explosion as one of the display cases, just a few metres away from them, burst apart. There had been a skeleton inside it, held up by a steel frame, but now it broke free and came lumbering out. It was hard to see anything clearly in the mist and the darkness but Matt could just about make out something that resembled a crocodile, long and narrow, with short, squat legs holding it just above the floor. It had thrown itself forward, smashing through the gla.s.s in a sudden, silent frenzy. The one thing it couldn't do was roar. It had no lungs. But its feet a bones without flesh a made a bizarre sound as they clacked against the mosaic floor. It was charging at them, its mouth gaping, its black teeth snapping at the air. Its tail thrashed behind it, scattering the fragments of what had once been its home.

The pterodactyl dived for a fifth time, its pointed beak aimed at Matt's head. With a cry he threw himself on to the floor, then rolled over and over again, avoiding the crocodile creature that had accelerated towards him, its jaws snapping. How could it even see, Matt wondered, with eye sockets that were completely empty? But it didn't hesitate. It turned round and came at him again. Matt was on his back. In seconds the creature would be on top of him.

Then Richard acted. He had grabbed a chair and, holding it like a baseball bat, he swung it at the crocodile, using all his strength. The heavy wood and upholstery slammed into the creature, knocking it off course and causing one side of its ribcage to collapse. It lay on the ground, twitching and rattling, still trying to get back on to its feet. Its mouth opened and snapped shut. Its head thrashed from side to side.

"Move!" Richard shouted.

A second showcase blew itself apart. Gla.s.s crashed down. One by one the dinosaur skeletons were coming to life. Bone rattled against marble. Matt got to his feet, wondering how many exhibits there were in the museum. And what about the one they had seen when they came in?

The diplodocus.

Even as Matt turned towards the huge creature, he saw the bones begin to tremble and knew that it too was coming to life. The diplodocus was twenty metres long. Its dreadful tail was coiling and uncoiling, animated by whatever energy was flowing through it. One of its legs moved, each of the joints shuddering. Its head swivelled round, searching for its prey.

"The door!" Richard yelled, then cried out as something crashed into him. It was a giant lizard skeleton, walking on its two hind legs, its arms outstretched. It was made up of at least a hundred bones suspended from a long, curving spine, with vicious teeth jutting forward, snapping at his throat. Richard fell backwards, his arms flailing. Matt saw the keys leave his hands and arc into the darkness. The lizard leapt into the air. Richard hurled himself sideways. The lizard crashed down. If he had waited one more second it would have landed on top of him. "The door!" He screamed the words again. "See if you can find a way out."

The mist was getting thicker and Matt could no longer see from one end of the hall to the other. There were further explosions, one after the other, as more exhibit cases were destroyed from within and half-visible shapes appeared, flying, strutting or crawling towards them. Richard was searching blindly for the keys. But perhaps the doors would open another way. Surely there must be a fire exit, or some way out in case of emergencies.

Matt ran the full length of the hall and reached the front door. Sliding to a halt, he grabbed the handle and pulled. The door was locked. Frantically he tried a second door. That was locked too. Looking out through the gla.s.s, he could see offices and flats across the main road. The traffic was moving as usual. Ordinary life ... but it could have been a thousand miles away. Both sets of doors had been locked for the evening. There was no emergency lever. They were trapped.

"Richard!" Matt called out. There was no sign of the journalist.