He was perched upon a plank which projected out from the side of the ship. The plank swayed with every movement of the ship. The Doctor's ankles and wrists were tied with rope. Heavy chains had been looped around his ankles and these were attached to what looked like a badly cracked cannon casing. Another rope was looped tightly around his neck.

This rope was tied to a high spar. Every movement of the ship threatened to pitch the Doctor from the plank, so that he would either drown or break his neck. Many pirates were gathered on the deck and more clung to the rigging. Most of them were laughing. Some were taking bets on how the Doctor would die. Every so often someone would fire a shot into the sky. The catcalls and sounds of drunken mayhem were loud and constant.

I crouched beside the mid-deck hatch, shrouded in darkness, and studied the positioning of the pirates that I could see. The man nearest the ship end of the plank was the most important. He held a cutla.s.s and was taunting the Doctor with it.

Reaching out beside me I found Topeno's hand in the yellow gloom and took his knife I checked the balance for throwing. I could not afford to miss.

I took one last look around me, gauged the distance, stood, threw Topeno's knife and immediately crouched back into the shadows. The knife flashed once in the yellow light as the blade bit into the spar an inch from the rope secured to the Doctor's neck.

I had missed.

I already had the second knife ready for throwing in case I had been seen. I was lucky. The knife was small and the black obsidian blade was not seen in the gloom.

My heart banging in my chest I prepared to make the second throw. I waited for the ship to come to an even keel, stood and threw again. The knife bit into the rope at the precise moment the man with the cutla.s.s jabbed the Doctor in the back. The Doctor wobbled, swaying as the ship continued to roll with the waves, trying to regain his balance. The men gave a mighty shout of glee as it looked like the Doctor would fall after all. Then three things happened at once. The Doctor regained his balance, the rope fell clear of the spar, and from somewhere nearby came the boom of a cannon.

Captain Stuart.

In seconds there was chaos. The cannon blast had snapped the mizzenmast at the height of the second spar. Sails, rigging mast, spars and all came smashing down into the deck, the wreckage bringing about thirty men with it. Most were knocked senseless; some fell into the water. In another moment a hundred islanders had scrambled aboard the ship, obsidian knives held in gleaming teeth, and the deck was awash with blood.

But the movement of the ship had caused the Doctor to lose his balance. He fell from the plank. Then, amazingly, he stopped, hanging suspended in midair. Like Jack and me in the cyclone, the Doctor was prevented from falling by the chains and weight, which had fallen from the other side of the plank and now acted as a balance to keep him from falling. He swung upside down from the plank - I thought I made out a bemused shout of surprise.

Then I saw the sailor with the cutla.s.s make for the ropes securing the plank to the deck. If he cut those the plank would fall, taking the Doctor with it to his death.

I ran for the pirate, who swung to face me, cutla.s.s outstretched. I drew my blade and threw it with one motion. The pirate fell, the cutla.s.s sc.r.a.ping the deck before jamming against the rail. I retrieved my knife and scooped up the cutla.s.s. Such a long blade was unfamiliar, but its reach would be useful.

The ship was now in an uproar. There were shouts and the sound of pistols firing. Screams lifted into the night. Another cannon blast sounded. This time the ship took the blast broadside at the waterline.

Smashed planking erupted into the air in a burst of flame and smoke. I saw three men impaled by smashed railing - two Peruvians and an islander. At the same time yellow flame gushed upward from the quarterdeck as the oil lamps which had been fixed to the smashed mizzenmast set light to the fallen shrouds.

I turned to the Doctor and ran out along the plank.

'Do you know, Leela,' he called from beneath me. 'I really hate hanging about like this. It's awfully boring. Can you get me free?'

'No.' I could not cut the chains. If I pushed them free of the plank the Doctor would fall. There was no way to free him without killing him.

Worse, my weight on the plank was bending it towards the sea. And the combined weight of the Doctor and the cannon barrel was dragging the chains in juddering movements along the plank. They were about two feet from the end. And the further they got the more the plank bent.

I heard the Doctor call, 'The chains are secured by locks. DaBraisse has the keys. Get the keys, Leela! It's the only way to free me.'

Without answering I leapt from the plank on to the deck, which by now was covered with fighting pirates and islanders. I looked around for DaBraisse, seeing nothing but flashing steel and puffs of smoke and flames. The cannon sounded again. I crouched, expecting the ship to roll as before, but there was no movement. The cannon were obviously being aimed at another ship. In confirmation I heard a ma.s.sive explosion to starboard. The fighting stopped momentarily as everyone turned to witness a nearby ship burst into flames.

'- hit the magazine -'

'- down she's going to -'

The ship took another broadside at the waterline and exploded violently, a vision whose light dwarfed the crescent moon easily. Her masts snapped, her sails blazing in the night, a rain of smoke and burning debris smashing into the water and the other ships anch.o.r.ed nearby. Above my head, debris slashed a trail of sparks and smoke through the mainmast rigging. The shrouds caught and the air was full of smoke. I turned as a pirate swung towards me, and threw the cutla.s.s. It turned in midair, striking the man and knocking him over. I leapt forward and cut his throat, moving on quickly before anyone else could attack me.

By now the fighting had renewed, with the added complication that men were leaping off the side to avoid the flames prowling like starving animals across everything that would burn. I wanted very much to join the fleeing men but could not. If I saved myself the Doctor would die. I had to find the key. And that meant finding DaBraisse. But how was I to do that? I could see only one chance.

I turned towards the foremast and began to climb the rigging. I knew my only chance of finding the pirate Captain was to try for a better view. I gained the first spar and tried to peer through the smoke and flames. I saw cook on the port beam throw a handful of pepper in a pirate's face and then bury his cleaver in the man's skull while he was trying to claw the stuff from his eyes. He waved to me as he pulled the cleaver free.

Then a shout from the starboard beam caught my attention. Someone was on the plank with the Doctor, pushing the chains along the plank so that he would fall off. At the same time I caught sight of a man moving with some purpose through the screaming sailors, cutla.s.s flashing and pistol spitting flame as he strode untouched through the smoke. This fellow wore clothes of a finer quality than the rest. And he moved as if he knew what he was doing. He had not succ.u.mbed to the panic aboard ship. It must be DaBraisse. But he was on the mid-deck and making for the port side. If I went to help the Doctor he would escape. And if I tried to get the keys to free the Doctor the pirate working on his chains would have the time he needed to drop the Doctor over the side. The man working at the Doctor's chains was too far away for me to throw a knife at. There was only one chance.

I ran lightly along the burning spar on which I was perched, cut away a long length of furling rope, lashed it to the end of the spar and threw myself off the mast. I screamed as I swung down from the spar, felt smoke rush into my lungs and scorch them. I screamed to get the attention of the man working to kill the Doctor. If I could distract him for just a second I would hit him and knock him off the plank. The man looked up as I hoped he would. His mouth opened in surprise as I flew through the air, past him, round in a big arc out over the water and back again, kicking him with both feet soundly in the head as I pa.s.sed, knocking him from the plank before spinning back across a deck now burning fiercely to smash against another pirate at the exact moment the spar from which my rope hung burnt through and smashed into the deck.

Clinging to the pirate I fell to the deck with enough force to knock the breath from me. I lost my grip on my knife, which skittered away across the deck. The pirate was on his feet in an instant, pistol levelled. I was staring at death. I knew what it was like to be shot and I wasn't looking forward to it happening again. But there was nothing I could do about it. I had no weapon.

I heard the shot before I felt it. In fact - I did not feel the impact at all.

I stood quite still, waiting to fall, waiting to die.

Nothing. Instead the pirate froze, an expression of astonishment crossing his face before he fell, to reveal Royston, holding a small pistol.

'You see, Leela?' He called with a grin. 'I told you could -' he stopped suddenly, coughed blood and fell to the deck - 'trust -' He blinked, rolled on to his side, and kicked feebly.

I saw the dagger emerging from Royston's side at the same time I saw the pirate captain staring at meat the same time as the foremast top spar began to fall, burning, to the deck.

DaBraisse. Pistol levelled. At me.

I moved fast, rolling across the deck as the spar fell, to smash into the deck between us. I heard the pistol discharge but once again felt no shot. I dived over the burning wreckage and wrapped my arms around DaBraisse's waist, and we both crashed to the deck. We rolled in flames.

My skin screamed. I felt his hands about my neck. But I wasn't trying to kill him. That could come later. I wanted the keys I had seen jangling at his belt.

I grabbed the keys, whipped them backwards into his face as his grip tightened about my throat. He screamed and rolled away from me.

Scrabbling for a weapon, he fell through a gap in the deckrail and vanished overboard.

Wasting no more time, I hurled myself through a wall of flame and on to the port deck. The Doctor was hanging, feet uppermost, at the very edge of the plank, which was cracking from the heat even as I ran along it.

The ship's movement made footing treacherous. As I reached the Doctor one of the chains slipped over the edge. He fell an arm's length closer to the water before jerking to a halt. I stretched downward to cut the ropes binding his arms and then reached for the locks holding the chains tight around the Doctor's ankles. I had the key in the lock when the boat rocked with another explosion and the chains slipped again. Now the Doctor was hanging upside down, his head under water and the locks at his ankles well out of my reach. In a few moments he would drown. But I couldn't reach the locks.

Desperately, I wound the loose chain around my own ankle and lowered myself head first from the creaking plank. It took me three tries to get the key in the lock, and each second our combined weight dragged the cannon upward and lowered us further into the water.

Then the lock sprang open with a rusty click and the Doctor plunged into the water. At the same time, freed of its balancing weight, the cannon fell from the other side of the plank, dragging me back upward and over the top with it.

Now I was hanging from the plank with the chain wrapped around my ankle, the cannon a muscle-cracking weight at my feet, a moment away from drowning myself.

Desperately I kicked my way clear of the chain and hauled myself back up on to the plank - just as it cracked through and began to fall.

I scrambled on to the burning deck as first the cannon and then the plank followed the Doctor into the bay.

I got up and tried to find a way across the deck. I had been wrong about Royston. He had saved my life. If there was the slightest chance he was alive I was going to save his in return.

The deck was almost completely burnt through and the ship was listing badly. The foremast was creaking dangerously above me as I used another rope to swing across to the port beam. Royston was where I had left him, tucked into a corner of the mid-hatch coaming. I could see much blood - but he was moving. I ran to him and scooped him up. He groaned.

Good. If he had the strength to protest he had a chance at life.

Holding Royston, I turned towards the port rail - it was on fire. There was no way off the ship there. The front of the ship was now a wall of flame and the deck was collapsing beneath my feet. I ran towards the stern of the ship, trying to find a way off. The deck was a maze of burning wreckage; the remains of the mid-and mizzenmast, the spars, burning shrouds, the dead bodies of islanders and pirates alike. I ran towards the stern. As I pa.s.sed the mid-deck hatch it blew into the air atop a fountain of flame. Part of the deck followed almost immediately. Burning debris peppered my back and hair. The ship's magazine had caught fire. I remembered the other ship exploding and ran faster, flames licking at my heels, the deck shaking and tipping under my feet so that I was running uphill, the smoking wreckage of spars and timbers and ropes falling around me like a burning spinner's web, until the stern rail appeared through the flames and, clutching Royston as if both our lives depended on it, I threw myself over the stern.

The ship exploded while we were still falling, the blast of scorching air lifting us further away from the ship. I remember seeing, while upside down, the mid-deck dissolve into flame. The remaining mast toppled, burning, smashing through the weakened deck and slicing the ship in half, allowing more air in to mix with the burning gunpowder.

A storm of wreckage erupted into the air as we hit the water. Taking hold of Royston, I dived as a deadly rain of burning timber smashed into the water all around us.

We now had one chance at life - and that depended on how long both of us could hold our breath.

25.

Virus

The Doctor explained what the Library had shown us.

'There were aliens who influenced the development of the culture on Easter Island. But they only did it by accident. They lived in a solar system - this system - many light years away, and were fighting their own great war at the time.'

'Losing the fight to their aggressors, they decided to preserve their race by launching great quant.i.ties of their own DNA into s.p.a.ce, preserved within support mechanisms controlled by intelligent machines. On arrival at a suitable world, the DNA would be introduced into a group of host organisms. This DNA would then attach itself to the host species'

DNA and remain dormant there, hidden from any inquisitive glance by the aggressor species.'

'The DNA would remain hidden as long as it took for the aggressors to leave the original system. When this happened a signal would be sent to the intelligent machines, now spread randomly throughout the galaxy.

The machines would use subsidiary extensions - what you know as the walking stones - to open and stabilise the negative ma.s.s of an Einstein-Rosen Bridge - a kind of tunnel through s.p.a.ce - and the individual members of the host species carrying the dormant DNA would be returned through the bridge to the original home system, where automatic systems would reactivate the dormant DNA and re-create the original species from the host individuals.'

'Obviously this would take thousands of individuals - so many of the intelligent machines were launched into s.p.a.ce. One came to Earth - to Rapa Nui - and influenced the culture there over the generations that it remained dormant. Hence stripping the island to build the - - a reaction to a buried race memory which may have slipped back into the islanders' a reaction to a buried race memory which may have slipped back into the islanders'

cultural patterns over the generations.' The Doctor thought for a moment and then added, 'So that's what happened to the thousands of islanders that have vanished over the generations: used as carrier pigeons for an alien amino-acid chain.'

I frowned. This was beginning to sound more than ever like the ramblings of a tortured mind. 'Doctor, I am a medical man, a man of science. I hear your words but I do not understand them. What is "DNA"?

What is an "amino-acid chain"? And what has it got to do with carrier pigeons? How can an individual be transformed into another? Surely that is akin to alchemy - and we all know how ridiculous that idea is.'

Now it was the Doctor's turn to frown. 'Yes, of course, stupid of me.

We're about a century too early for DNA, aren't we?' He thought for a moment. 'All right, think of it like this: you're fighting a war and you want to send important messages to your men at the front.'

'Yes.'

'But you can't send them in plain English because your enemy can read English.'

'Yes.'

'So what do you do?'

'Why, send them in code of course!' The moment the words pa.s.sed my lips I understood the Doctor's a.n.a.logy.

The Doctor beamed. 'It's so simple. The aliens had encoded themselves. themselves.

The islanders were their message. The rongo-rongo rongo-rongo was the cipher wheel used to encrypt the message and the was the cipher wheel used to encrypt the message and the moai moai the means of transmitting it.' the means of transmitting it.'

I looked at Horace. He was smiling - he understood, too. Even Richards's expression showed a dawning realisation.

Only Leela seemed puzzled. 'If they were so clever, why are they still dead?'

The Doctor began to pace. 'A good question. Anyone know the answer? James?'

I hazarded a guess. 'Either the encryption details were lost or the message became corrupt.'

The Doctor nodded, displaying the absent-minded pleasure a schoolteacher might take in a promising pupil. 'Or the encrypted message was re-encrypted.'

'I don't understand.'

'The library mentions a plague. And it seems clear to me that the surviving structures within this culture are not as old as the culture itself.

Someone must have been alive to build or maintain them.'

'But who?'

'Well, it's my guess that the plan worked and many thousands of carrier organisms were returned through various wormholes from many different planets to this system. Enough to begin reseeding the race. Then disaster struck: one carrier organism returned with an additional virus - one unknown and lethal to the original species. A plague. One which wiped them all out for a second time, leaving just the intact structures and cultural remnants we've all seen, the oldest site being the factory world where the original were built and launched into s.p.a.ce.'

There was a moment's silence as we all considered the Doctor's tragic hypothesis.

'But which of the thousands of host organisms carried the virus?'

Horace asked in a whisper.

'According to the library, the last host organisms arrived here about thirty years ago - and originated from Earth.'

Horace said quietly, 'You mean we we killed them?' killed them?'

The Doctor nodded.

I said, 'The Polynesians are an isolated culture - those on Rapa Nui even more so than most. It's possible they have not been exposed to certain diseases. Visitors to the island could have brought anything from measles to smallpox - any one of which might have been lethal to the islanders or carried in a dormant form when they returned here. Do you remember telling me Tortorro's son suffered from a fever? Well, that might have been given to him by one of the men on your ship - someone who displayed no symptoms of the disease himself.'

'I see.' Horace's voice seemed to shrink. He licked his lips. 'I think I'm going to go for a walk if you don't mind. I think I need some air.'