They need not have worried about the fissure being concealed by the snow. It split the moorland like a jagged cut, a wide, dark, serrated hole. There was no snow either side of the fissure for several feet, and the gra.s.s that poked through the rocky ground looked dry and dead.

Dobbs knelt at the edge of the snow and felt the bare ground beside the fissure.

'Warm?' the Doctor asked.

'Warm enough for the snow not to settle.'

'Hmm. Deep then,' the Doctor commented. He took a step closer to the edge, leaning forward and trying to peer into the depths of the hole. Wisps of smoke were curling from the abyss and rising, twisting into the sky.

'We can worry about the depth later,' Dobbs decided. 'First we should plot its size and position on a map. Mr Gaddis, if you would be so kind?' He held out his hand.

'What?' Gaddis had been watching the Doctor. 'Oh, of course' He pulled the satchel from his shoulder and opened it. From inside he took a folded map of the area.

Dobbs relieved him of the map and opened it out, holding the large paper flapping in the light breeze. The Doctor turned back from the fissure, the wind ruffling his hair as it rippled the map.

'How do you propose to plot it?' he asked. 'Looks about, what, ten feet across? We'll have to find the ends to work out its length. And it may be changing of course.'

'We can check that,' Gaddis a.s.sured him. 'We'll take bearings on each end today, then again tomorrow and see if they have changed. Try again in a week and we should know if there's any movement and how rapid it is.'

The Doctor pursed his lips together, sucking in his cheeks. 'Not much by way of precise landmarks for triangulation,' he observed. 'If you want an accurate measurement.'

'There is the dam,' Dobbs pointed out. 'And the church spire.'

'The mine too, if that's what it is over there.' Gaddis nodded as he reached inside the satchel again.

Dobbs and the Doctor both looked where Gaddis had indicated. Sure enough, Dobbs could just make out a few low buildings huddled together, brown wood just visible through the snow that clad them and masked their shape against the hill that might have been material worked out from the mine.

'I think perhaps your idea of precision is a little different from mine,' Dobbs heard the Doctor murmur. He ignored the comment and took the compa.s.s from Gaddis.

But any irritation was lost as he watched the needle. 'How very peculiar,' he said. He gave the instrument a little shake and looked again. 'What have you been keeping with this?' he asked Gaddis. 'Nothing magnetic, I hope?'

Gaddis frowned in surprise. 'Of course not, Professor. Is there a problem?'

Dobbs held out the compa.s.s. 'Indeed there is '

Gaddis reached across to take back the compa.s.s, but the Doctor beat him to it, lifting it from Dobbs's surprised hand and turning immediately away.

'Excuse me,' Dobbs exclaimed.

'Doctor, may I?' Gaddis reached out again.

The Doctor remained oblivious to them both. His attention was focused on the compa.s.s. He stared intently at it for several seconds, then swung suddenly round, never taking his eyes from it. Moments later he was bounding across the landscape, keeping parallel to the fissure, Gaddis and Dobbs trailing in his wake. He stopped at last, licked his finger and held it in the air. Then he shook his head in apparent irritation and drew a heavy sigh.

'Doctor, the compa.s.s,' Gaddis said, annoyed. 'If I may have it, please?'

'Oh, of course.' He tossed it towards Gaddis, and turned away again towards the fissure, as if he had completely lost interest. 'It won't tell you anything,' his voice floated back.

The compa.s.s had landed in front of Gaddis, upside down on the damp ground. Dobbs watched as the younger man picked it up and brushed the surface with the side of his hand. It took him only a second to see that the Doctor was right. The needle of the compa.s.s was spinning, turning back and forth, unable to settle on a single direction.

'What does it mean?' he asked in surprise. 'Professor?'

Dobbs shrugged. 'It is as if there were another magnet nearby,' he said. 'Sufficient to divert the needle from pointing North.'

'But why does it swing back and forth so alarmingly?'

'Of course it's a magnetic influence.' It was the Doctor who replied. He was still staring at the fissure, facing away from the others. 'It swings because the magnet the Professor postulates is so large.'

Dobbs coughed, a way of showing both amus.e.m.e.nt and disbelief. 'But there is nothing here, Doctor. Nothing so large that it could exert such an influence.'

'Unless...' Gaddis walked slowly over to join the Doctor. 'Do you mean...?'

The Doctor waited until Dobbs had joined them, staring down at the smoky hole, before he answered. 'Exactly,' he said in a low voice. And despite the warm air he could feel rising from the fissure in front of him, Dobbs shivered.

'I have come across,' Gaddis said slowly, hesitantly, 'some sites, usually ancient sites, where there seem to be lines emanating. Under the surface. Hidden.'

'Lines?' Dobbs asked: What do you mean, hidden lines? If they're hidden, how do you know they're there?'

'You can... feel them. That's the only way I can describe it.'

Dobbs snorted in derision. 'Feel them! How scientific an observation is that?'

'Go on,' the Doctor said gently. He shot a glance at Dobbs, remonstrating.

Gaddis shrugged. 'Well, that's it, really. I don't know what they are. I just wondered ' He shrugged again.

'Whether we might not have some similar phenomenon here?' the Doctor finished for him. He was nodding vigorously. 'Good thought, good thought.'

Dobbs had listened to enough of this, and could contain himself no longer. 'It is not a good thought,' he exploded. 'Mysterious invisible lines of goodness*only*knows*what '

'Magnetic influence?' the Doctor suggested.

Dobbs ignored him '- snaking out across the landscape from a perfectly natural fissure caused by seismic activity. Utter nonsense, Mr Gaddis. And I'm surprised you even give it credence, Doctor,' he added.

'I take it you are not convinced.'

'No, sir. And even if I were, I struggle to understand how we would test this theory or what we should make of it were we able to test it.' Dobbs folded his arms, daring one of them to answer.

It was Gaddis who spoke first. 'I have found that dowsing gives a good indication of the path of '

'Dowsing?' Dobbs stared. Was he hearing correctly? 'Dowsing?!'

'What's wrong with dowsing?' the Doctor asked, his voice making the question sound reasonable.

'Ancient old wives' balderdash without a shred of scientific foundation or experimental value, not testable or verifiable in any way.' Dobbs paused for breath. 'Is that a serious question? What's wrong with it?'

The Doctor seemed unperturbed by Dobbs's outburst. 'Yet you were willing to consult a compa.s.s,' he said. 'How very eccentric.'

Dobbs drew himself up as tall as he could. hands on his coat lapels as he looked down his nose. 'There is at least one eccentric person here,' he said, his gaze flicking from the Doctor to Gaddis and back, 'quite possibly two. And I am confident that neither of them is me.' He waited for this to sink in, and then added: 'Now, let us have no more talk of such idiosyncratic methods and confine ourselves to observable, verifiable science, shall we?'

'Don't argue with him, Doctor,' Gaddis said, his eyes fixed on Dobbs. 'Once he gets like this, there's no reasoning with him.'

'Reason, sir, has nothing to do with parading across the countryside with a pair of sticks in front of you,' Dobbs snapped back.

'I've observed as much myself,' the Doctor replied. But Dobbs was not sure which of them he was agreeing with.

'So let us instead decide what we should do in the absence of a reliable compa.s.s. Hmm?'

'You can do what you like, Professor,' Gaddis said. 'Despite your blinkered comments, I intend '

'I think,' the Doctor interrupted loudly, 'that we should go for a walk.'

They both stared at him. 'Go for a walk,' echoed Dobbs.

The Doctor nodded. 'That's the spirit. Yes, exactly. To see if we can discover the extent of this natural seismic phenomenon. Don't you think?'

'You two do what you like,' Gaddis said again. 'I intend -'

'To see how far the fissure extends that way? Off towards Ambleton?' the Doctor finished for him. 'Very wise. The Professor and I shall see how far towards the dam it reaches. Won't we?'

This last was addressed squarely at Dobbs. He blinked, frowned. He tried to think of a response. But in all honesty this did seem like the best plan. 'Of course, Doctor,' he said. 'Just what I was about to suggest myself. We shall observe this phenomenon and measure it as best we can. Then meet back here to compare notes at, when shall we say, noon?'

'An excellent plan, Professor,' the Doctor said clapping an arm round his shoulder and leading him along the edge of the thawed snow. 'See you later, Mr Gaddis,' he called back.

Professor Dobbs did not bother to look back. He did not particularly want to see if Gaddis was mirroring their progress, walking back beside the fissure. He was not interested in what Gaddis might be doing. And he regretted that for the rest of his life.

The fissure narrowed to a crack as they progressed. After about half a mile, it petered out, the light covering of snow rea.s.serting its supremacy over the landscape.

'Have you ever encountered anything similar, Doctor?' Dobbs asked as they stood at the end of the fissure and looked back along its length.

'Not that I recall.'

'What do you suggest now?' Dobbs was not used to deferring to others, particularly anyone younger than himself. But the Doctor exuded a sense of experience, of confidence.

'It would be useful to get an overall impression,' the Doctor said. 'If we could see it from above...'

'From above?' Dobbs frowned. 'Really, Doctor, unless you have a hot air balloon readily accessible I doubt whether that would be possible.'

'Oh I don't know.' The Doctor was looking past Dobbs, staring into the distance. 'A vantage point would suffice, I think.'

Dobbs turned to see where the Doctor was looking. 'A good thought,' he conceded. 'From the top of the dam we should be able to examine the extent of this trench.' He peered into the distance. There seemed to be some movement on top of the dam, tiny dots of colour moving back and forth behind the railings that ran along its length. 'I do believe there is someone up there already,' he declared. 'Sightseers, perhaps?'

'Soldiers,' the Doctor said.

'Soldiers? But why? What can they be doing?' Dobbs turned back to the Doctor. But he was gone. He looked all round in a sudden panic, had the Doctor vanished into thin air? But no, he was striding out across the frozen landscape towards the dam.

'Why don't we ask them?' he called back to Dobbs as he went.

Dobbs hefted his walking stick and followed.

From the top of the dam the figures were two small black dots, ants making their way across the snowy moorland. Colonel Wilson watched the tiny figures as they approached. He was leaning on the iron railings that ran along the top of the dam. The metal was cold even through the leather of his gloves.

'Do you know them?' he asked Captain Brookes. The figures grew closer and there could no longer be any doubt that their destination was the dam.

Brookes produced a set of field gla.s.ses and examined the two men through them. Then he handed the gla.s.ses to Wilson. 'Can't say that I do, sir.'

'Nor I,' Wilson agreed as he watched them reach the base of the dam. The younger man started up the service ladder set into the side of the structure, close to the rock wall that delineated the cutting through which the river had run. 'Griffiths!' he shouted, waving the sergeant over. He pointed at the figures making their way up the ladder. The older man was being left behind by his more agile partner. 'Find out who they are and what they want, would you?'

'Of course, sir.'

Leaving Sergeant Griffiths to worry about the newcomers, Wilson turned his attention back to the work. Another hour, would you say?'

'The lads are just double*checking the last section, sir. Then we have to pack up the equipment. Two hours at the most.'

On the other side of Brookes, Wilson could see the first of the two men climbing off the ladder to stand on the walkway at the top of the dam. He was talking with Sergeant Griffiths, pointing out across the moors, back in the direction he can come from. As they conversed, the older man heaved himself up beside them, almost exhausted, the air misting as he breathed out heavily.

Wilson sighed, and made his way along the dam.

'Bracing isn't it, Colonel,' the younger of the men called out as he came within earshot. The man's long hair was blown back from his face by the wind and his jacket was billowing out behind him.

'It is indeed, sir,' Wilson agreed, surprised that the man recognised his rank. 'A couple of the men have lost their caps in the reservoir. It's actually quite calm now, but it can kick up a fair storm when it sets its mind to it. Quite bracing if you happen to be hanging over the side on a rope, I can tell you.'

'I'm sure.'

'May I ask your business here, sir?' Wilson said. Though he was prepared to be civil and polite, he was not really in the mood for a chat about the weather. He nodded a dismissal to Griffiths, and the sergeant seemed relieved to be on his way.

'Do we need any?' the man asked. 'And do you need to know if we do? I a.s.sumed this was public property.'

Wilson regarded the man closely. His tone was not unpleasant, and his eyes were alive with intelligence. Maybe it was just his manner that made him seem insolent. 'Your business is your own, of course, sir,' Wilson conceded. He had to be careful, he had no idea who this man was or what position he might hold. He did not recognise either of the men as locals, and that in itself marked them out. 'But we are currently checking this structure to ascertain whether its integrity has been damaged by recent events. Under the circ.u.mstances...' he let the implications hang.

The man c.o.c.ked his head to one side as he listened. Then he nodded towards the dark gash of the fissure than ran across the landscape below them. 'By recent events, I take it you mean that.'

'And the tremors, sir, yes.' He decided on a different approach. 'May I at least ask you your names?'

It was the older man who replied. He seemed to have got his breath back now after the climb. His voice was authoritative, but tinged with respect. 'Of course. I am Professor Isaac Dobbs of the Royal Society, and this is...' He waved a hand in the air as if hoping the name would come to him. 'The Doctor,' he said at last, his tone suggesting that this much was self*evident.

'We're very interested in recent events, as you call them,' the Doctor said quickly as Dobbs finished. 'In particular we wanted to take a look at that fissure from up here. Get an idea of the size and shape of it.' He leaned closer to Wilson. 'Make deductions and test a.s.sumptions,' he added knowingly.

Scientists, Wilson could cope with. He was an engineer himself by profession an engineer and a soldier so he had an appreciation of the sciences. 'I see, Doctor. Well, please help yourself to the view. My men are just finishing, but if we can offer any help or insight which might be of a.s.sistance, please do ask.'

'You're very kind,' Dobbs a.s.sured him.

'Is it safe?' the Doctor asked.

'Sorry, sir?'