“Luckily, children,” said Mr Blake, “a friend has come to help you.”

They looked where he was pointing. To their right was a ditch, then a bank, with a hedge at the top. The bank was overgrown with flowers and weeds – bluebells, grasses, brambles, celandines, anemones and young bracken – but towards the top, between two twisty hedge-roots, was the entrance to a little tunnel, and in the entrance was a brown mouse, with a pinpoint of light in its eye.

"Quickly,” whispered Mr Blake urgently. “Jump the ditch and climb up to him.”

"But that's just a mouse!” said Dora.

“Yet see how he waits for you,” said Mr Blake.

The mouse did seem to be waiting: instead of scampering into the darkness it held itself almost completely still, except for small attentive movements of its ears and the constant trembling of its whiskers.

“One of the help cards is a mouse,” said Adam.

“And to me he looks like a friend,” said Mr Blake.

The black car had landed by this time, and the four men in old fashioned clothes, who didn't seem to see it, were still hurrying towards them. The red-coated soldier was closest.

“Go on!” urged Mr Blake.

“Are you coming with us?” said Dora.

“No. But perhaps we will meet again in due course.”

Adam took Dora's hand. “Come on!” he said.

They jumped, and scrambled up the bank on the far side of the ditch, which seemed to grow as they climbed it. Soon they were holding on to the stems of bluebells and ferns to pull themselves up, and scrambling over twigs the size of small tree-trunks, or beneath bramble-arches with thorns as long as daggers. The mouse waited until they were close, then vanished into its tunnel. But it left its tail trailing in the entrance. Dora was holding Adam's hand to help him up a difficult bit, and reached out with her other hand to grab something and steady herself, and found herself holding the tail, which was muscular, bristly and warm.


Next moment, the mouse must have scampered a few steps, because the tail suddenly dragged them upwards – Dora's arm was almost wrenched out of its socket, and she nearly let go of Adam's hand - but they were both inside the tunnel.

“Ouch!” said Adam. “I banged my knee!”

“At least we're safe,” said Dora. They could hear shouting from outside. “They can't follow us in here, can they?”

“I don't think so,” said Adam. “But it might be a place for black beetles.” She felt his hand tighten on hers as he spoke.

They both peered ahead into the gloom. The mouse was looking over its shoulder, as if to check where they were. Then it set off, pulling them forward into the darkness. It smelt of earth and mouse-droppings. At first there was a little bit of light from the entrance, but soon it was pitch black.

Within a few minutes they were hot and exhausted and longing for the journey to end. They were about the same size as the mouse, but it had designed its tunnel to be run along on all fours, which meant that it was too low for Dora and Adam to walk upright. They either had to bend double and crook their knees, or – in places – to crawl. Whatever they did, their heads kept bumping the ceiling, which meant showers of dirt going into their hair, their eyes, their ears, their mouths, and down their backs. Another problem was that the tunnel didn't run straight, but kept twisting up and down and from side to side, perhaps to get past massive hedge roots, which they could often feel in the walls. And on top of all that, the mouse didn't keep to an even pace. It would scamper along one moment, so fast that it was almost impossible to keep up; then stop; then scamper again.

Dora would have let go of the tail almost immediately, except that every few steps she could feel an empty space to her right or left, with a flow of cold air coming through it. Those must be the entrances to other tunnels. They must be threading through an underground maze, and if she lost hold of the mouse they might never be able to find their way out again.

“Do you have to keep rushing and stopping like that?” complained Adam when the mouse was having one of its breaks.

“It's not me – it's the mouse.”

“Can't you slow it down?”

But the mouse was off again, and there was nothing Dora could do except stumble and scramble after it. She never would have thought a mouse could be so strong.

“I'm ever so thirsty,” moaned Adam at the next pause.

“Me too.”

“I'd do anything for a drink of water.”

“Try not to think about it-”

There was a scrambling, pattering noise.

“Oh no!” cried Dora.

“What's wrong?”

“The mouse – it's gone without us!”


“It's your fault!” she shouted. “I was thinking about water, because of you – so I stopped holding its tail properly - and then -”

“You idiot! Shut up and follow it!”

They rushed into the blackness as fast as they could. At every moment Dora was half-expecting to bump into a furry back – or perhaps a whiskery nose, if the mouse had returned to look for them – but it never happened. They blundered through the dark for what seemed like ages, with their hearts thumping and the sound of their own laboured breathing in their ears; but then they slowed; and eventually flopped down against the walls of the tunnel.


“This is terrible!” said Dora. “What if we can't find our way out?”

“What if we die of thirst?”

“What if we're lost in here for ever?”

“What if a black beetle comes?”

“I wish I'd never seen that stupid puzzle box.”

“Why don't you get it out, and have a look?” suggested Adam. “See if it can help us.”

“What good's it going to do in here? I won't even be able to see the cards.”

“True,” said Adam. “You'll probably drop them and lose them.”

“No, I won't! Anyway, I suppose I might as well try. It can't do any harm.”

“Well, for goodness' sake be careful.”

“Of course I'll be careful.”

“You weren't very careful with the mouse's tail.”

“Shut up.”

She took out the box, placed it on the floor of the tunnel, and opened the lid. To their delight, a faint silvery-blue glow came from within, like starlight but stronger. The children crouched forward eagerly, then stared open-mouthed at one another's sweaty and filthy faces.

“You look terrible.”

“So do you.”

“Is the light coming from the cards?”

Dora took out one of the cards and held it up. “I don't think so,” she said. “It's just coming from – inside the box – somehow.”

“Cor,” said Adam. “I've never been so glad to see anything. I'd be even gladder to see a drink of water, though.”

“Come on then,” said Dora, getting up as well as she could under the low ceiling. “We can't sit here for ever, or we really will die of thirst. We'd better get moving.”

“Don't let the cards fall out,” warned Adam. “Who's going to carry the box?”

“I am, of course.”

“Why can't I carry it?”

“Because it's my box!”

“Can't we take it in turns?”

“All right,” said Dora. “We'll take it in turns. But it's my turn first.”

She led the way. Inwardly she was wondering what they would do if they came to a crossroads or a fork – how would they make up their minds which way to go, without the mouse to guide them? Could they somehow mark the walls, in order to find their way back if they needed to?

But the difficulty never arose, because there were no further side-tunnels. And what's more, the one they were in was changing its character. Instead of twisting from side to side and up and down, it was now more or less straight, and it went downwards quite steeply. The walls were further apart too, and the ceiling was higher. Before long they could walk upright and side by side.

“I don't think the mouse made this,” said Dora.

“Nor do I,” agreed Adam. “And he definitely didn't make those,” he added a moment later.

Just in front of them, the tunnel ceiling suddenly sloped downwards even more steeply than before, and the rough floor was replaced by a flight of steps.

“Well,” said Dora, “at least we seem to be getting somewhere. Nobody would have made these steps unless they led to something.”

They started to descend.

“Have you noticed that it's getting colder?” said Adam.

“It's partly because we're not rushing any more.”

“But it's not just that,” said Adam. “It's freezing. You can see your breath.”

Dora opened her mouth experimentally and breathed out in a big gasp. Sure enough, a cloud of soft silvery vapour curled in the air for a moment in the faint light from the box.

They went down and down, and the air got colder and colder.

“We must be getting deep under the ground,” said Dora.

“I thought it got hotter when you went down deep.”

“That's only when you get right to the middle of the earth.”

“Are you sure? What about volcanoes?”

“Well, what about permafrost?”

“Perma what?”


“I've never heard of it. There's no such thing.”

“Yes, there is!”

“Well, what is it, then?”

“It's... sort of... I don't know, really. I heard Dad talking about it once. I think it's like a cold layer, under the ground, that never melts.”

“Not even when there's a volcano?”

“Oh, stop going on about volcanoes!”

“Well, at least I know what they are.”

“Shush!” said Dora. “Listen!”

They were at the bottom of the stair. After the last step came a few feet of level passage, then an archway. Beyond the arch, instead of a continuation of the tunnel, there was blackness; and out of the blackness came a low whispery noise. It kept stopping and starting. First there would be a long faint hissing or scraping, like a dead leaf being pulled slowly across a stretch of sand; then a slight pause; then the same sound again, going back the other way.


Instinctively they held hands, and stood listening for a long time, on the bottom step, while the whispering noise came and went outside. When Dora spoke, at long last, she felt obliged to whisper too.

“It couldn't be the sea, could it? Could there be an underground sea?”

“I hope not,” whispered Adam in reply. “How would we ever get across it?”

They listened for a bit longer.

“It's too slow to be the sea,” muttered Adam eventually. “And it sounds too dry.”

“What can it be, then?”

“Could be the wind.”

“Then why does it keep stopping and starting like that?”

“Well, we're never going to find out by standing here. We'd better go and have a look.”

“But what if it's something moving about? What if it's something alive?”

Adam tugged at her hand. “Come on,” he said. “The mouse must have come this way, mustn't it? And we're meant to be following the mouse, aren't we?”

“All right,” said Dora; and they walked to the end of the tunnel.

Beyond the archway, the passage floor seemed to continue, but the walls and ceiling disappeared. By the faint light from the box they could just make out a few feet of path straight in front of them. Above them was darkness. To either side of the path, more darkness. And from the feel of the air, they could somehow tell that they were now surrounded by a huge empty space.

“I think we're in a cave,” said Adam.

“But where does the path go?” said Dora.

“I think it's a bridge,” said Adam.

Dora suddenly realised that it wasn't just dark to either side of the path: it was empty. They weren't at the bottom of the cave: they were halfway up one of its walls. They might be hundreds of feet in the air. It felt as if the bottom had dropped out of her heart. She clutched hold of Adam's arm.

“I can't go across that,” she said.

“It's all right,” said Adam. “It's quite wide.”

It was easily wide enough for the two of them to walk next to each other: but the top wasn't flat, it was curved; and it wasn't smooth either, but craggy and twisty.

“Do you know what I think?” said Adam. “I think it's a giant root! Imagine what the tree must be like! It must be absolutely enormous!”

Dora was hardly listening. She kept imagining herself tumbling off the edge of the root, and falling helplessly into the darkness below.

“There are no sides! There's nothing to stop you falling off!”

“You won't fall off. It's much too wide. Just keep hold of my hand.”

“No, Adam, I really don't think I can do it. I really don't think I can.”

“Come on, Dora. We can't just turn round and go back. We're meant to be following the mouse. The mouse must've come this way, mustn't it?”

“I suppose so.”

“Come on, then. Keep hold of my hand.”

“All right,” said Dora. “Okay. All right. You take the box.”

Adam took the box in his right hand, and she clutched hold of his left arm.

“Don't look down,” he advised.

“I'm not looking anywhere,” said Dora. “I'm looking at your shoulder. That's all I'm going to look at.”

They edged forward. While they had been inside the tunnel they had longed for it to end; but now, when it came to leaving it, they felt as if they were leaving all the comfort and security of the known world behind. The emptiness yawned. The whispering noise didn't get any louder, but it surrounded them. There was a tiny lit-up stretch of path in front of them. Apart from that, nothing.

Dora stared at Adam's shoulder. It'll be over in a minute, she thought. It'll be over in a minute. It'll be over in a minute.

“We're there,” said Adam.

She dared to look. Just beyond his shoulder, straight in front, was a craggy, creviced wall. She let go of his arm, pushed past him, touched the wall, flattened herself against it, pressed her cheek against it, closed her eyes and drew a deep breath. She was safe.


“You nearly knocked me over,” complained Adam. “I could have fallen off the edge.”

“Sorry,” whispered Dora.

“Well,” said Adam, “now we've got some more steps.”

Reluctantly, she opened her eyes to look. She and Adam were standing on a rough kind of landing where the bridge met the wall. To their right was a descending flight of steps, which seemed to have been carved from the craggy substance of the wall itself.

“All right,” she said, “come on. Give me the box.”

The flight of steps wasn't nearly as wide as she would have liked, but she would have gone down one half as wide and twice as steep, if it meant reaching a solid floor.

“Wait for me!” hissed Adam.

“Well, keep up,” she replied. “I want to get down.”

“So do I,” said Adam, “but you've got the box, and you're blocking out most of the light from it. I can't really see where I'm putting my feet.”

“Is it my imagination,” whispered Dora, stopping for a moment, “or is that sound getting a bit louder?”

“It's getting louder as we go down,” confirmed Adam.

Dora went more slowly after that. She imagined something huge sweeping backwards and forwards across the floor of the cavern in the darkness. An enormous blind insect or a monster, sweeping the floor very softly with a feeler or a tentacle, first one way and then the other.

“And the air's getting colder, too,” whispered Adam. “I'm absolutely freezing.”

“So am I.”

They came to the bottom of the steps. The floor of the cavern was completely smooth and glossy, like black marble. By the light of the box they could make out a patch of wall and a patch of floor, nothing else. Deep inside the floor was a reflection of the light from the box, chilly and distant-seeming; and a shadowy suggestion of their own figures, upside-down. Everything else was huge cold darkness. The whispering sound was louder, more pervasive, but otherwise unchanged.

“Where do we go now?” whispered Dora.

She stepped onto the floor, and immediately slipped.

“Be careful of the cards!” hissed Adam.

“I couldn't help it!” protested Dora, steadying herself against the wall. “It's really slippery! It's like ice!”

Adam, still on the bottom step, crouched down and touched his fingers to the floor. “It is ice,” he said. “No wonder we feel so cold. We'll have to be careful how we walk. Sort of slide your feet along slowly.”

“But where shall we go?”

“Follow the wall for a bit,” suggested Adam.

It seemed the most obvious thing to do, so they did it, slowly and softly, sliding their feet and touching the wall with their left hands as they went. And within a few yards they came to another archway. Inside it, when Dora held out the box, they discovered a short stretch of level passageway, then more steps leading upwards.

“Thank goodness for that!” whispered Dora. “I'll be so glad to get out of this cave.”

“Wait a minute,” muttered Adam. “Just lend me the box for a moment.”

“What for?”

“Can't you hear that?”

“Oh, what is it now? I can hear that whispery noise, but apart from that -”

“Shush! That was it again! Didn't you hear it that time?”

“No, I -”

“Sh! Wait.”

She was silent, holding her breath: and out of the darkness came a new sound.

“A drip!”

“Yes, and it's nearby too. Aren't you thirsty?”

“Yes I am. I'm absolutely desperate.”

“Come on then.”

Holding hands, they edged into the blackness, away from the passage door. They didn't have far to go. Something silvery plummeted through the air in front of them; there was the sound of a drop hitting water; and ripples shivered in the blackness at their feet.

They went down on their knees. They were on the edge of a big puddle or a small pool. They scooped up water with their hands and drank. It was so cold that their teeth and throats and the bone between their eyebrows ached, but it was also delicious.


“That's the loveliest thing I ever tasted,” said Dora. “Now let's get back to that passage.”

She had put the box on the ice between them. Adam picked it up.

“Wait a minute,” he said. “You stay here. I just want to go and have a look-”

“Oh no, Adam,” hissed Dora, clutching his arm. “You're not going off and leaving me in the dark. I won't let you.”

“I've just got a feeling that there's something out there,” said Adam, staring into the darkness. “I almost thought I saw something just now.”

She clutched his arm even harder. “What sort of thing? Something moving? Was it something moving about?”

“No – it was – well, I didn't even see it, really. It was more like I felt it. It was something big and solid. Like a – I don't know – like a building or something.”

“Like a building,” murmured Dora slowly. In spite of herself she was intrigued. “Are you sure?”

“Well, no, not really. But it definitely wasn't anything moving. I just sort of got the feeling that something was out there.”

“All right then,” whispered Dora. “Go and have a look, if you really want to. I'll stay here, by the pool. And you mustn't go more than ten steps.”

“Twenty steps.”

“No, not twenty steps. That's too many.”

“Fifteen steps, then.”

“All right. Fifteen. But you've got to be quick, and you've got to come straight back.”

She gave him the box, and stayed kneeling on the ice, shivering, while he crept into the darkness. As soon as he left her she had a terrible sense that he was the one staying still, and she was the one floating away, into an icy black emptiness, losing contact with the little island of light which was the only solid thing she knew. How far was he going? He must have taken more than fifteen steps already.

But then he stopped. The light was shining against – something. She couldn't see what it was. His silhouette was in the way. Then he turned, and came back towards her. The light from the box lit up his face, and he was smiling an excited smile.

“You'll have to come and look!” he said. “It's fantastic!”

“What is it?”

“It's like a wall, but all different colours. Come and see!”

She followed him. It was really only a few steps. There was another wall – or sort of a wall – and as the light approached it, colours ran across it in ripples, rainbow colours, like the colours on a peacock's neck, blue and green shot with ruby, charged with an inner glossy electric blackness. The children could almost see their own reflections in the wall, but not quite. They reached out and touched it – carefully at first – but then patting and rubbing it. It was hard and shiny, dry and a little bit rough, all at the same time. Also, it wasn't quite flat. For one thing it bulged towards them slightly; and for another it had a pattern of ridges running through it, as if it were made of thin plates overlapping one another.

“I wonder how far it goes?” said Adam.

“Oh, Adam – don't you think we should be getting a move on? We're meant to be following the mouse, aren't we?”

“Yes, but don't you think this is worth seeing?”

“The colours are lovely,” she admitted.

“And it's such a funny wall, isn't it? What's it made of? And what's it doing here, at the bottom of a cave on a sheet of ice? It must be here for a reason. Can't we just walk along it a little bit?”

“All right, but just a little bit.”

They followed the shining wall. It was slightly curved. First it curved away from the side of the cavern: then it curved back again. Then it changed. It bulged. It wasn't a wall any more: it was a thing: some kind of big lumpy shape, at least as big as a house. And the whispering sound was louder. This was the source of the whispering sound.

“Let's go back!” said Dora, pulling Adam's arm.

“Yes,” he said, but he didn't move. He still had the box, and he lifted it up as high as he could. “Why's it shaped like this? What's it meant to be?”

“Come on!” said Dora urgently.

“Yes, all right. In a minute.”

Very unwillingly, she let him pull her a few more steps, then another few, as he tried to make it out. It was very difficult to get a proper impression of it, seeing it bit by bit in the light from the box. A corner, a blunt end, a sloping top. Sort of a wedge shape. Out of the blunt end came another smaller wall.

“It's like a – it's - it's like a -”

But it was Dora who guessed it.

“It's a snake's head!” she whispered suddenly.

The jumbled edifice transformed itself inside them. The wedge shape was the shape of a snake's head. And the smaller bit of wall -

“It's got another snake's tail in its mouth!” shouted Adam.

“Sh!” said Dora.

But she was too late. The whispering sound stopped. The silence was deafening. Then it came back again, a hundred times louder, a long rasping hiss: the sound of a snake drawing breath. And in the darkness, in both directions, they could hear, and feel more than hear, the body of the snake stirring, like a sinew stirring in the earth.

Adam grabbed hold of Dora's arm, and they ran for their lives. The box-lid snapped shut and they were in the dark, slipping and sliding, falling and scrabbling, slithering and scrambling. Somehow they were back at the rough wall, fumbling desperately for the exit. Huge shockwaves went rolling through the blackness behind them.

They lurched forward into a gap. The archway, the passage, the steps. They pounded upwards as fast as their legs would carry them, but within minutes their muscles were turning into jelly. They didn't know if they were being followed or not. The gasping of breath and the pounding of hearts was all they could hear. They tried to force themselves onwards, but it was no good. Their legs gave out completely. They flopped down onto the steps, running with sweat and crowing with exhaustion.


After a while the darkness stopped leaping and pulsing in time to the thumping of their hearts, and their breathing went back to something like normal.

“You idiot!” were the first words Dora could manage.

“Me!” croaked Adam. “It was your fault!”

“How can it be my fault?”

“Sh!” said Adam. “Is it following us?”

They listened, but they couldn't hear anything.

“It couldn't get in here anyway,” said Adam. “Too big. Lucky I got us in here so quickly.” He opened the box carefully, and the blue-silver light leaked out.

“Give me that,” said Dora crossly.

Reluctantly, he pushed it towards her across the step.

“From now on, I'm never going to let you hold it.”

“Oh, shut up.”

“I bet you dropped some of the cards.”

“Course I didn't.”

“I bet you did.”

“Well, why don't you check them, then?”

She did so, grumpily; but as she did it her bad temper dissolved; and she held up one of the cards for him to see.

“Look,” she said.

It was the one that showed a snake with its own tail in its mouth.