Prologue

"THE weather in the far north of Ireland will continue unsettled for at least the next twenty-four hours," came the crackly voice of the radio weatherman. "… occasional outbreaks of rain and northeasterly winds gusting up to forty knots…"

The rest of the marine forecast dissolved in a hiss of static that was lost in the roar of twin Yamaha outboards and the slap of water against black and orange sponsons as the big inflatable boat punched through the waves off the north coast of Donegal. Irish Fisheries Officer Mick Scanlan grimaced as he scanned ahead with a pair of powerful marine binoculars, one arm looped through the boat's A-frame to brace himself. Amidships, sitting astride the pillion seat behind the control console, his partner, Lorcan O'Haverty, throttled back slightly to compensate for the wave chop.

The sky overhead was a dirty shade of grey, looking more like February than early May, and the two officers were dressed for weather. With their bright orange crash helmets and regulation life-vests, both men wore the distinctive orange-and-black survival suits called Polar Bears that could keep a man alive for several days in these waters, whose winter temperature often dipped to near-Arctic levels. Even in May, though the water had begun to warm, hail and sleet might accompany the squalls and storms so prevalent in this area. To be caught out unprepared could be fatal.

Not that today was too bad, as days went in early May. The wind was brisk, but the sun looked poised to break through the cloud cover for at least a little while. A hundred yards off to port, the outbound tide was peeling back on itself lethargically from the sheer base of a long line of sea-cliffs, leaving the exposed rock-faces festooned with streamers of stranded kelp.

Scanlan shifted his weight and continued to scan. Off to the seaward side, shadowed and uncertain under the receding tidewash, the dark lurk of submarine rocks posed a threat to conventional craft venturing in this close, but the rigid inflatable boats used by the Irish Department of the Marine drew only inches of water, and had proven highly effective for this kind of patrol. Weighing hardly more than a ton, a six-meter boat like this one could be trailered where needed and launched within minutes - a godsend for men like Scan-Ian and O'Haverty, charged with protecting the coastal fishing rights of a country heavily dependent upon its maritime industries. While much of their routine work was done ashore - either shuffling reports in the local fisheries office or else conducting routine inspections on the docksides of fishing ports from Inishfree to Malin Head - field investigations were not at all uncommon.

This morning they had launched from Downies to check a report of illegal fixed nets in the area. Their backup boat had developed engine trouble and would try to catch up later, but their land-based backup would be shadowing them from the shore in a Land Rover, also linked by radio. Scanlan had spotted him as they passed Dunfanaghy, and expected to pick him up again after they rounded Horn Head.

The radio chatter ebbed and flowed against the background bluster of wind and waves, and Scanlan automatically scanned the shoreline as O'Haverty skipped their nimble craft past a succession of small inlets gouged out of the coastline by the action of the North Atlantic tides. But as O'Haverty brought the boat around the point of the headland, a sudden and unexpected stretch of calm water stretched before them along a narrow crescent of sandy beach adjacent to the rock cliffs. Taking closer notice now, Scanlan saw that the outbound swells were coated with the greasy rainbow film of spilled oil.

"Uh-oh," O'Haverty said, glancing back at him.

"Yeah, I see it." Scanlan swung his binoculars along the sweep of shoreline and adjusted the focus. "We'd better have a closer look."

As O'Haverty nosed the boat toward the beach, the slick became visible as a V-shaped stain fanning out across the flattened waves, apparently coming from a waterline cleft in the base of the cliffs that marked the western end of the beach.

"Looks like it's coming from those rocks up ahead," O'Haverty said.

"Yeah." Scanlan lowered his binoculars for a few seconds to peer with unassisted sight, then resumed his study. "I don't see any signs of a wreck, though. Maybe an oil barrel's gotten washed against the rocks and broke open. Let's go in, and I'll check it out."

Without comment, O'Haverty brought the boat around with a spin of the wheel and gave a brief rev to the engines to propel them in toward the shore while Scanlan shed his binoculars and helmet and moved into the bow, ruffling a hand through sandy hair. As soon as the boat's snub nose nudged sandy bottom, Scanlan threw a leg over the side and stepped onto the sand and shingle, grabbing an anchor and coil of line. Sea water washed and tugged at the legs of his survival suit until he won free of the retreating surf and bent to set the anchor behind a cluster of rocks a few yards higher on the beach. Behind him, O'Haverty pulled up the slack and snubbed it off.

"We'd better make this quick," O'Haverty called, shouting to make himself heard above the boom of the surf. "Tide'11 be turning soon."

Grinning, Scanlan gave his partner a thumbs-up sign and turned to begin trudging toward the promontory. The tide-lines to his left suggested that the strip of beach was only exposed to view at low tide - which explained why he did not remember having seen it before, even though he and O'Haverty had passed this headland many times on routine patrol. He was halfway to the base of the cliffs, heading for the area from which the oil seemed to have come, when a flicker of color and movement drew his gaze upward.

About halfway up the cliff-face, a small flurry of sea gulls exploded into flight from the mouth of a jagged fissure in the rocks. That alone was hardly surprising, but as the birds wheeled away screeching, a slight, shaven-headed figure in flowing orange robes suddenly appeared from behind them.

The sight was startling enough to bring Scanlan up short, to send him scuttling into the shadow of the cliff-face to his left - though if the man looked down, he was sure to notice the bright orange upper half of Scanlan's survival suit. Scan-Ian could not have said why it seemed important that the man not see him. Even as he craned to get a cautious better look, hardly able to believe his eyes, a second man emerged from the fissure's mouth, a slightly more wizened version of the first. Both were well past middle age, and obviously of Oriental extraction.

What the hell? Scanlan thought.

Their attire reminded him of the Hare Krishna votaries he had seen now and again in Dublin and London, handing out flowers and pamphlets on street corners or dancing and singing in the streets - except that these two were much older than the usual Hare Krishna, and far less scruffy-looking. Part of the difference lay in the high-collared black tunics they wore beneath the saffron-orange outer robes, almost like a priest's cassock - a feature that Scanlan couldn't recall ever seeing before. But that sartorial difference paled to insignificance before the incongruity of anyone so garbed being present on this bleak, windswept stretch of Donegal coast.

The two glanced back into the darkness of the cave and conferred briefly, whatever words they spoke whisked away in the wind and the boom of the surf, then moved off along a ledge that slanted away toward the landward summit of the cliff. As they disappeared behind a screen of boulders, they seemed not to have noticed that they were being observed from shore and boat.

Scanlan backed away toward the water's edge, trying to discover where the pair might have gone, but he could see no trace of them. More mystified than ever, he shifted his puzzled gaze back to the mouth of the cave. What could they have been doing in there?

Glancing back at O'Haverty, who lifted both arms in an exaggerated shrugging motion, Scanlan waved a hand at his partner in a gesture to stand by, and started up the rocks. He unzipped the neck of his survival suit as he climbed, reaching inside for the small but powerful emergency torch he always carried. The cave warranted a quick look.

He gained the ledge without mishap, sidling carefully along it till he reached the narrow cave mouth. After a last glance over his shoulder to assure himself that O'Haverty was still watching from the boat - and scanning the cliffs beyond with the binoculars - Scanlan ducked into the opening and switched on his torch, poking the powerful beam back into the darkness.

The cave appeared to extend some distance into the cliff-face. The dank iodine-tang of the seashore prickled at his nostrils as he started edging forward, scything the beam of the torch before him as his eyes began to adjust to the darkness. A dozen cautious steps took him to the brink of deeper darkness, where his torch probed out across the echoing vault of a much larger cavern.

The vaulted expanse was not wholly dark. Here and there pale lances of daylight pierced the shadows, filtering down through scattered chinks in the roof and the seaward wall. The cave alone was unusual enough, but not far below, the sweep of his torch and the fugitive glimmers of daylight picked out the dark, deadly outline of a great torpedo shape slumbering in the gloom, with a more angular shape thrusting upward from the center. It almost looked like - good Lord, could it be? - a beached submarine!

"Jayzus, Mary, and Joseph!" Scanlan muttered under his breath.

His words echoed in the confines of the sea cave like an untimely intrusion in the hush of some vast cathedral. He fell silent as he played his torch along the length of the thing, noting the faint gurgle of water stirring sluggishly about its armor-plated flanks. The sound suggested that the cave itself was accessible to the tides from outside, but he could see no other openings above ground save the one through which he himself had just come. Nor could he make out any underwater glow that might indicate a passage below the waterline to the sea beyond.

"Jayzus," he breathed, more softly this time. It was difficult to make any very accurate estimate of the sub's size, but he guessed she must be close to two hundred feet long, maybe more. She looked like all the photos his father had shown him of German U-boats he had helped to sink during the Second World War, when he served on a British frigate. The lines of her were right, from the graceful, deadly bow, with its jag-toothed net-cutter and lethal torpedo tubes, to the stubby conning tower and snorkel, to the deck guns mounted fore and aft. And just readable, as he played his torch across the slight curve of the conning tower, was the white-painted designation 636.

U-636. He wondered how she had come to rest here. What little he could see of her did not appear to be damaged. And she must have been lying here in secret for nearly half a century.

Suddenly avid to have a closer look, Scanlan hunkered down and flicked his torch over the rocks below, seeking a way down. A narrow ridge meandered gently along the side, slick with sea wrack but perhaps rendered less treacherous by a profusion of barnacles. A series of outcroppings presented him with a ready-made set of stepping places and handholds, and should bring him within a few feet of the foredeck.

Exhilarated at the prospect of exploring the vessel, he hooked his torch to a clip on his life-vest and began his descent toward the cavern's watery floor. The air in the cavern was moist and heavy, the tang of brine laced with a musky hint of something else that reminded Scanlan curiously of church incense. The water lapping along the hull looked to be perhaps waist-deep. He was not quite sure whether the tide had turned yet, but he should have a few minutes in reasonable safety.

He reached the bottom of the cavern without mishap and sprang lightly to the sub's foredeck, unclipping his torch to play it before him as he started aft. He brushed one hand along the rusted length of the sub's big 3.5-inch deck gun just before he skirted the conning tower, again shining the torch on the painted numbers, 636. The ladder going up into the back of the conning tower was heavily rusted, but it looked sound enough - and was.

He climbed carefully, lest he cut his hands or damage his suit, and emerged on the command bridge. Forward, the wheel that dogged down the hatch drew him almost irresistibly, but when he tried to shift it, it stubbornly resisted his efforts.

"Shit," Scanlan muttered. Though he had not really expected it to open, he still was disappointed. Panting a little from the exertion, he shone his torch around the inside of the conning tower again and noticed something he had missed in his first inspection: an irregular grey packet about the size of his two hands, lashed to the inside of the nearest bulkhead by grey webbing straps.

The straps fell to bits as he tried to loose the buckles. The packet itself was sheathed in a double layer of oilskin, mildewed and brittle with age, that cracked and all but disintegrated as he peeled it back to expose a folded bundle of scarlet material. It was musty and damp, but when Scanlan gingerly shook it out, the mass of red became a German Kriegsmarine flag - red and black and white.

He caught his breath at the sight of it - once-fine scarlet wool boldly ensigned with the distinctive black cross of old Germany behind the newer white roundel and black swastika of the Third Reich. He almost dropped it in sheer reflex, for the associations of evil that it held.

Again he found himself wondering what might have brought U-636 to her present resting place. His first thought had been that her captain must have been using this cave as a base from which to sally forth and harry Allied shipping. That seemed unlikely, though, for he could not imagine that the cave had ever offered safe access to and from the outside.

Had she fled here for sanctuary, then, pursued by her enemies? Again, how? He recalled hearing how stragglers from North Atlantic wolf packs sometimes had taken refuge in the depths of Tory Sound, not far away, though far more subs had ended up on the bottom than had escaped. He had even heard tell of a German sub from the First World War, said to lie on the floor of Donegal Bay, farther south. In those days, German submarines had used mercury for ballast - lots of it. There was talk of trying to salvage that ballast, for mercury in such quantities was extremely valuable; and such a salvage might also avert a later rupture, with its accompanying ecological implications.

Belatedly, he remembered the oil slick he had seen from outside. Surely this was its source. Had the sub limped here damaged, then? Shining his torch along her off side, he could see nothing overt, but who knew what lay below the waterline? More probably, however, the slick he had seen could be attributed to a leak in one or more of the fuel tanks, their fabric failing at last after five decades of progressive deterioration.

But why had she been beached here in the first place, and how? More mysterious still, now that Scanlan stopped to think about it, was the matter of the two Hare Krishna types he had seen emerging from the cave. Recalling them now, he wondered what possible connection such individuals could have with a German submarine. What were they even doing in this part of the world? - in Ireland, of all places. Had they stumbled across the cavern purely by chance? Somehow Scanlan doubted it.

A gurgling sound like the lapping of waves recalled Scanlan from his speculation, and he flashed his torch over the side again. The tide had turned. The water level in the cavern was rising - further confirmation that there must be an underwater channel leading to the outside. He had better get out of here, if he didn't want to get trapped or maybe even drowned.

Clipping the torch to his vest again, Scanlan set about refolding the flag. He was well aware that the sub's presence would have to be reported to the proper authorities. After this long, her salvage value was probably nil, but if she still held torpedoes, there was no telling how unstable they might have become in half a century. And there was the oil-spill question; who knew how much fuel might still reside in her tanks, set to trigger yet another ecological disaster?

In the meantime, however, there was no reason why Scanlan should not take the flag for himself as a souvenir. Stuffing it into the front of his survival suit, up under his life-vest, he zipped up again, then swung himself down out of the conning tower and set about retracing his route to the exit.

The grey light of the overcast day seemed glaringly bright after the dimness of the cavern's interior, even though a heavy fog bank had begun to roll in with the incoming tide.

Scanlan emerged squinting from the cave and fetched up short as his half-dazzled gaze picked up a blur of bright orange out on the ledge a dozen yards to the landward side of the cave entrance.

Even as Scanlan gasped, the blur resolved itself into one of the Hare Krishnas - or maybe he was some sort of Oriental monk, come to think of it - gazing expectantly in his direction. Startled, Scanlan looked around for the second one and spotted him down on the beach below, standing ankle-deep in the water right next to the boat, a brighter orange against the deeper shade of the inflatable craft. He could not see O'Haverty.

"Hey, what are you doing?" he shouted, gesturing with his torch toward the man in the water. "Lorcan, where are you?"

O'Haverty did not answer, but the second monk glanced up at him with placid indifference. Only then did Scanlan realize that both men were holding odd-looking daggers with heavy, triple-edged blades, perhaps a foot long overall. The weapons looked dull and clumsy, hardly capable of inflicting much damage unless one were hit over the head with the pommel, but Scanlan found himself gripping his torch more tightly, wishing it were bigger, heavier. He had never heard of Hare Krishnas being other than peaceable and nonviolent, but there was something not right about these two. And where was O'Haverty?

Almost without realizing what he was doing, Scanlan began to back away from the nearer monk. As he did so, the one down on the beach thrust his dagger into his belt and jerked loose the anchor that was holding the boat in place, beginning to gather in the mooring line. His movement gave Scanlan a clearer look at the interior of the boat - and the crumpled splash of black and brighter orange lying in the stern, awash in a sea of crimson.

"Lorcan?" Scanlan whispered, the color draining from his face.

The monk in the water paid him no heed, merely continuing to coil the mooring line. The fog bank swallowed up the sun in that instant, and the temperature seemed to drop by at least twenty degrees.

Before Scanlan could summon the will to move, to do something, the monk on the ledge turned his impassive gaze back to the cave from which Scanlan had just emerged and clasped the hilt of his dagger between his palms, point downward. Then, as the thin lips began to move silently, the agile hands began rolling the hilt of the dagger between the palms, the black eyes quickly losing focus and rolling back in the hairless head. As Scanlan edged away from the man, trying to decide which one was the greater threat, the monk on the beach tossed the anchor into the bow of the boat and moved back amidships. His expression, as he turned his face toward Scanlan, was one of mild reproof.

"Curiosity can be very costly," he announced, in heavily accented English.

He must have done something to the boat's controls then, for the engines suddenly roared to life, the bow swung around, and the boat began heading away from the shore.

"Hey!" Scanlan shouted, starting to skitter down the ledge in pursuit.

Even as he said it, already aware that he had no chance of catching the retreating boat, the monk up on the ledge raised the point of his dagger toward the entrance to the cave, continuing to roll the hilt between his palms - and suddenly released the weapon.

It sprang from between his hands, launching itself through the air like a tiny guided missile to strike the top of the cave opening with explosive force. With a crack like a thunderclap, the rock above the opening gave way, raining down rubble to bury the passageway under a descending weight of earth. Within a matter of seconds, the cave mouth had vanished, erased under tons of broken stone.

The concussion staggered Scanlan to his knees. Now nearly to the beach, he scrambled up and wheeled around in time to see the strange dagger come flashing back to its owner's hand like a boomerang.

Scanlan's eyes flew wide in blank incredulity. Even as his mind groped in vain for a logical explanation for what he had just witnessed, he realized that the second monk now was rolling his dagger the same way the first had done - except that its point was directed right at Scanlan!

The sight made Scanlan's blood run cold. Backing off a few steps in horror, he turned to bolt for the imagined safety of a tumbled ridge of boulders, skirting close to the edge of the cliff-face. A lightning scramble up over the rocks took him some distance above the level of the beach. But before he could take shelter behind any of the outcroppings, the monk on the beach released his dagger.

Running for his life, Scanlan had no further warning before the blade thudded home between his shoulder blades, piercing to the hilt. The pain transfixed him as he screamed and staggered, his torch flying from his hand as he toppled forward into the sea. His head cracked against a rock enroute and he knew no more. Where he landed, the water for an instant was dyed crimson, but then the surf took command, dispelling the red as it rolled his body to and fro.

For a moment the monk on the beach gazed impassively at the tumbled form, at the occasional glimpse of the dagger's hilt protruding from the bright orange of his victim's survival suit - which would not permit its wearer to survive this assault, no matter its sophistication. When the monk raised his hand in a gesture of summons, the dagger pulled itself free with a slight shudder and snapped back to the summoner's hand like the flick of an adder's tongue. Briefly the dagger pointed again at Scanlan, and his body caught an eddy of current and began to drift eastward, against the direction of the incoming tide.

The monk nodded and turned his back on his work, scanning for his companion. Up on the cliff-face, the other monk was picking his way back down to the beach, having finished inspecting his handiwork. Of the former cave opening, only a tumble of rubble now remained, indistinguishable from all the other tangle of rockfall on this face of the promontory. Offshore, the blank wall of incoming fog had already swallowed up the sight and almost the sound of the retreating boat, and the smaller speck of the floating body's life-vest and survival suit had very nearly disappeared.

The monk from the cliff rejoined the one on the beach. Facing eastward, the two stood shoulder to shoulder and prepared themselves, daggers grasped in their right hands with the blades pointed downward toward the sand at their feet.

Together they began to mouth the words of a whispered chant, faster and faster, until abruptly the eyes of first one and then the other rolled upward in trance. Faces rapt, lips still moving, they then set out along the shrinking beach in a series of lengthening bounds.

They gathered speed as they went, their pace accelerating to carry them forward in smooth, fluid leaps, each one longer than the one before. As they travelled, the two made rhythmic, forward-reaching motions with their right hands, driving their dagger-points toward the ground as if propelling themselves off the surface with the aid of unseen walking sticks. They struck out across the water when they came to the end of the sand, just skimming the flat surface for half a dozen strides, their movements blurring into invisibility just when they would have disappeared into the fog beyond.