Riptide

The corners of St. John's lips lifted in what might have been a smile. 'If I had two months, I'd be happy to give it a try. But I don't. Besides, I have no idea how long a key he was using, if any, or how liberally he'd strewn his nulls.'

'Nulls?'

'Nihil importantes. Letters that don't stand for anything, but are tossed in to confuse the codebreaker.'

A boat horn sounded outside, deep and mysterious, and Hatch checked his watch. 'It's ten,' he said. 'I'd better go. They'll be sealing the flood tunnels and draining the Water Pit in a few minutes. Good luck with Kerry.'

Chapter 19

Leaving Base Camp, Hatch began jogging up the path toward Orthanc, eager to see the new structure that had materialized over the Water Pit in just forty-eight hours. Even before he reached the crest of the island, he could make out the glassed-in observation tower, a narrow deck running around its outer edge. As he drew closer, he could see the massive supports that suspended the derrick almost forty feet above the sandy ground. Winches and cables dangled from the underside of the tower, reaching down into the darkness of the Pit. My God, Hatch thought. They must be able to see this thing from the mainland.

With this, his thoughts drifted back to the lobster festival and to what Clay and his old teacher had said. He knew that Professor Horn would keep his opinions to himself. Clay, though, was another matter. So far, public sentiment toward Thalassa seemed overwhelmingly favorable; he'd have to be careful to keep it that way. Even before the festival had come to a close, he'd spoken to Neidelman about giving Donny Truitt a job. The Captain had promptly added him to the excavation crew that would start digging at the bottom of the Water Pit as soon as it was drained.

Hatch approached the derrick and climbed the external ladder. The view from the observation deck was magnificent. The ever-present mist was breaking into tatters under the hot summer sun, and he could just make out the dark purple stripe of the mainland. The sun glinted off the ocean, turning it the color of beaten metal, and the surf broke over the windward reefs, surrounding them with spume and a line of drifting wrack. A phrase from Rupert Brooke surfaced unbidden in his mind:

The little dulling edge of foam

That browns and dwindles as the wave goes home.

He raised his head at the sound of voices. On the far side of the observation deck he could see Isobel Bonterre, her wetsuit shining damply in the sun. She was leaning over the railing, twisting the excess water out of her hair and talking animatedly to Neidelman.

As Hatch strolled over, she turned to him with a grin. 'Well, well! The man who saved my life!'

'How's your wound?' Hatch replied.

'De rien, monsieur le docteur. I was out diving this morning at six, no doubt while you were still snoring the loud snores. And you will not believe what I have discovered!'

Hatch glanced at Neidelman, who was nodding and puffing on his pipe, clearly pleased.

'That stone foundation I found on the seabed the other day?' she continued. 'It runs along the inside wall of the reefs, all around the southern end of the island. I traced the remains this morning. There is only one explanation for it: the foundation to an ancient cofferdam.'

'An ancient cofferdam? Built around the end of the island? But why?' Even as Hatch asked the question, he realized the answer. 'Jesus,' he exhaled.

Bonterre grinned. 'The pirates built a semicircular dam all along the southern reefs. They sunk wooden pilings, arcing out from the shore into the shallow water, then coming back to land again, like a stockade fence in the sea. I found tracings of pitch and oakum, which they probably used to make the pilings watertight. Then they pumped out the seawater, exposed the sea floor around the beach, and excavated the five flood tunnels.

When they were done, they simply destroyed the cofferdam and let the water back in. Et voila, the traps were set!'

'Yes,' Neidelman added. 'Almost obvious, when you think of it. How else could they build underwater flood tunnels without the benefit of scuba gear? Macallan was an engineer as well as an architect. He advised on the construction of Old Battersea Bridge, so he knew about shallow-water construction. He undoubtedly planned all of this, down to the last detail.'

'A cofferdam around the entire end of the island?' Hatch said. 'Sounds like a huge task.'

'Huge, yes. But remember, he had over a thousand enthusiastic laborers to do it. And they had enormous chain pumps from the bilges of their ships.' There was another blast from a boat horn, and Neidelman checked his watch. 'Fifteen minutes until we blow the explosives and seal those five flood tunnels. The mist is clearing nicely; we should have a fine view. Come on inside.'

The Captain ushered them inside Orthanc. Beneath the windows that lined the walls of the tower, Hatch could see banks of equipment and horizontally mounted monitors. Magnusen and Rankin, the geologist, stood at stations in opposite corners of the tower, while a couple of technicians Hatch didn't recognize were busy wiring and testing components. Against one wall, a series of screens showed closed-circuit video feeds from around the island: the Command Center, the mouth of the Pit, the interior of Orthanc itself.

The most remarkable feature of the tower was a massive glass plate that occupied the center of the floor. Hatch stepped forward and gazed down into the maw of the Water Pit.

'Watch this,' Neidelman said, flicking a switch on a nearby console.

A powerful mercury arc lamp snapped on, its beam stabbing down into the darkness. Below, the Pit was drowned in seawater. Bits of seaweed floated in the water and brine shrimp, attracted by the light, jerked and played just below the surface. A few feet into the murky water, he could make out stumps of old timbers, heavy with barnacles, their ragged lengths disappearing into the depths. The fat, metal-jointed pump hose ran along the ground and over the side of the Pit, joining half a dozen other, narrower cables and feeder lines.

'The throat of the beast,' Neidelman said with grim satisfaction. He swept his hand over the consoles ranged beneath the windows. 'We've equipped the tower with the latest remote-sensing equipment, including L-band and X-band synthetic-aperture downward-pointing radar. All with dedicated links to the Base Camp computer.'