I collapsed, arms outstretched, hands inches from him. The ground seemed to shake underneath me.

The woman moved, I thought I saw her hand curl around the gun to hold it in place against her head. The gun began to smoke. Her voice was quiet now, almost inaudible. But her body was making other sounds. Other melting sounds.

Chris's finger tightened on the trigger. He was going to do it. Oh Benny, he was going to - The night lit up around us? Torches. Figures in s.p.a.cesuits with lighted helmets, guns and sprays shooting clouds of ice-cold, choking moisture.

One of the figures seemed to have three eyes.

I looked across at Benny in the light from the torches, and almost screamed again.

It wasn't her.

It was horrible. The woman was in her fifties. She was wearing what looked like a pressure suit. Her hands and face were exposed? Blisters covered almost half her visible skin surface. The rest was blotched. Some was peeling away. Her eyes were squeezed tightly shut. Shiny tears emerged from the corners and cut smoking tracks through her cheeks.

But she wasn't Benny. Wasn't Benny! She could still be alive. I felt an overwhelming sense of relief.

Then the woman opened her eyes and stared up at Chris. I gasped. One eye was almost intact; the other was a mess of milky fluid and blood. She grasped the gun more firmly, her gaze locked on Chris. 'Shoot me. Kill me.

Now. Please. Please!' She coughed blood. The coughing turned into another scream. 'Please!'

But Chris could only stare? The gun shook in his hand. In both their hands.

The barrel smoked as acid attacked it. Chris muttered something - I thought I heard him say Roz Forrester's name.

But still he waited.

'I can't,' he muttered.

'G.o.d almighty, Chris, she's in agony! For G.o.d's sake do as she says!'

Chris seemed about to answer but was interrupted as a voice boomed in the darkness?

'DROP THE GUN. THIS IS NATO COMMANDER JEREMY FIELDING. I HAVE AUTHORIZATION TO USE LETHAL FORCE TO RECOVER THIS.

ARTEFACT. I REPEAT: DROP THE GUN AND MOVE AWAY FROM THE.

BODY OBEY NOW OR WE OPEN FIRE.'.

Chris hesitated another moment, then put the gun down. The fact that his own skin must be burning as well seemed not to register.

The figures approached then. All we could do was watch them put the gun and the woman into separate plastic bags and carry them away?

I seemed to hear her moans in my head for a long while after she was gone.

They put us into a big military chopper and flew us out of the area? We flew for a short distance and then landed. We were taken out of the chopper - which was then sprayed heavily with what was obviously some kind of very strong industrial disinfectant - and from there marched towards a tracked vehicle.

The vehicle was obviously some kind of mobile HQ. It was wide and tall, with independent motors on either side to drive four sets of treads. It looked like nothing more than four double-size tanks connected by a rigid structure of gantries and Quonset huts. It must have been fifty metres wide, twice that long and about two storeys high. Spotlights and instrument packages were bolted haphazardly to the frame. An uplink antenna clunked slowly around on the vehicle's roof, pointing at the sky. I wondered at that for a moment - then realized that the vehicle was moving forward, very slowly, chewing its way across the floodlit rock, overhanging the road on either side by many metres. I wondered why we hadn't seen it when we'd overflown the area. Then as we were marched up to the entrance I saw a huge helicopter land and disgorge another mobile section from its cargo area. The section snuggled up to the front of the vehicle and was clamped in place. The helicopter flew off.

We were taken to an airlock; our clothes were removed and we were sprayed with disinfectant. The clothes were put into sterile bags marked with LEVEL FIVE: HOT MATERIAL stickers. I nodded to Chris. Thinking back to South Africa, I said, 'Level One is safe. Level Four is the Ebola virus. No known antidote.' He nodded but said nothing. The bags were taken away by suited figures.

After the decontamination we were taken along a corridor lined with UV lights and irradiated. After that came a number of injections. After that a skin scrub. After that we were forced to inhale a pink gas that made me sick. The vomit was placed into bottles marked LEVEL FIVE: HOT MATERIAL and taken away. After that the whole process was repeated.

'Ivice.

Disinfection apparently concluded, we were led to a room which resembled a miniature hospital ward, given a set of plastic coveralls and shoes and left to our own devices. We waited there an hour, while the floor swayed gently underneath us with the motion of the vehicle.

When the hour was up four suited figures came in and gave me the most thorough and embarra.s.sing medical I had ever been subjected to.

Finally, two hours after my original infection, if that's what it was, doctors, if that's who they were, treated me with painkillers and alkaline solution for the acid b.u.ms on my hand.

About once every five minutes during this process I demanded loudly to know if they had found Benny, where she was, if she was still alive, what was happening to her.

Apart from directing terse medical questions at us, n.o.body spoke a single word during the entire time we were being examined.

Their examination complete, the doctors left the room. While we were dressing another suited figure entered. The name FIELDING, E? J.

appeared on a name badge. I peered through the visor of his helmet.

Fielding was grey-haired, green-eyed. He looked very tired. Or perhaps very scared. He put a LEVEL FIVE: HOT MATERIAL bottle containing what seemed to be vomit down on the table in front of us. He took off his helmet, folded it neatly and placed it in a pocket of the suit. Then he unlatched the top of the HOT MATERIAL bottle and opened the lid.

'You're not infected. Your clothes are contaminated to Level Five and lethal, but you're not infected. You care to explain that?'

So we told him all about it. Well, I told him all about it. Chris said nothing.

Neither of us mentioned the Doctor. We just told him we were part of an archaeological expedition investigating possible resting sites of Noah's Ark.

I told him I was married and demanded to know if his people had found Bernice.

'Bernice?'

'Yes! Bernice Summerfield. My wife. I want to go and look for her.'

'Well you can't. We have a situation here, in case you hadn't noticed. A Level Five situation.' The way he said 'Level Five' drove a spike of fear right up into the base of my brain. I shuddered.

'I don't care! I have to = 'I couldn't give a bra.s.s monkey's b.a.l.l.s what you "have to ", Mister!'

Fielding's voice snapped out like a whip. 'This is the deal: I am in charge.

You do as I tell you. Non-compliance will be met with lethal force. Do you understand?'

I nodded slowly, trying to hold back tears. It was all just too much.

Chris said, 'You've told us we're not infected. Not infected with what? I'm trained in forensics. Perhaps I can help you.' Fielding sighed. 'Forensics? A copper, eh? They say when cops go bad they're the worst. Well, you can help all right. But I guarantee you won't enjoy it.'

He spoke into a microphone. Another figure entered the ward. A huge figure that dwarfed even Chris, with three eyes and green skin. I studied the Earth Reptile quietly. 'I didn't think you guys were moving openly in society yet,' I said by way of an opening gambit.

It was a dumb thing to say. Fielding jumped on it immediately? 'Imorkal, I want you to interrogate these two. Find out how they know sensitive information like that. Find out how they come to be immune when their clothes are lethal. Do it fast. We're depending on you.'

Imorkal nodded thoughtfully, his crest dipping. His central third eye opened slightly, peering at us with cold intelligence? Imorkal looked at Chris. He fell over. The gaze raked over him. Chris was gibbering quietly. I realized he was telling them everything that had happened to us, everything we had done since he had arrived in Turkey. Chris shut up. It wasn't enough.

Imorkal turned his gaze on me. I felt something reach into my mind. Felt a presence there. Something cold, inhuman, terrifying. Something that reached into my memories and dragged them out so that I experienced every moment of the last few weeks in excruciating detail, love, fear, hope, terror, all crammed into a few minutes' garbled mumbling?

When it was over I sat on the floor, shaking, trying desperately to get my breath back.

Imorkal turned to Fielding. 'They know little. They are here by accident?

They are immune because they were given the serum. They are telling the truth. They are not terrorists? They are innocent.'

'Is there any more serum?' 'They are not aware of any.'

'And the hypo was empty.' Fielding thought for a moment. 'All right. Thanks, Imorkal. And look - I'm really sorry about Liz. You know we'll save her if we can.'

Imorkal nodded? There seemed to be a significance to the exchange which I couldn't fathom. But then I was going to have difficulty working anything out for a while after the going over I'd just had.

Fielding issued a few more orders. A number of orderlies came in and helped us on to the beds. One of them was quite pretty. I was beginning to feel better already; attention from a pretty orderly couldn't help but speed up the process?

When we were settled, Fielding said, 'All right. Sony to have been so harsh on you. We've made a mistake here. We need to sort a few things out.' He seemed to make a decision. 'All right. Answers then. But first, I'm sure you want something to eat? Orderly, I'd like tea and some food brought to OpCon. Oh, and will you please remove that vomit before we have to fumigate the place? It smells like something crawled in here and died.'

OpCon was located on the upper deck and comprised one room filling what must have been fully a third of the available s.p.a.ce in that deck. Here the vehicle's motion was exaggerated. The front part of the room looked very much like the inside of a s.p.a.cecraft: consoles, operators, the quiet hum of machinery and the odd curse as someone spilt their coffee. The rear section, part.i.tioned by movable screens took the form of a cla.s.sroom, with half a dozen small desk-chair combos facing a bank of monitor screens and, incongruously, a blackboard mounted on a wooden easel.

Fielding led us through the forward section, getting reports as he went.

'- ground stable. Reaction negative -'

'- proceeding north north east. Rate three KPH -' '- ground stable. Reaction negative -'

'- sensor sweeps indicate biological infection total = '- human life signs negative. Terrestrial life signs negative - '- ground sensors on red one. Reaction positive A sudden flurry of activity?

'- elevated sulphur levels? Elevated carbon monoxide levels -'

'- me the d.a.m.n coordinates = '- ground reaction accelerating by ma.s.s '- where the h.e.l.l is it -'

'- all around us. It's everyd.a.m.nwhere it's - '- going to - '- deploy belly shielding - '- reaction off the scale -'

'- the h.e.l.l out of here - '- gonna have to ride -'

'- it's going to blow it's going to -'

There was a tremendous explosion somewhere off to one side? The ground shuddered and the HQ shuddered with it. Fielding ignored the shaking, motioned us through to the rear section.

The shaking subsided, the ground stopped swaying and HQ plodded on forward.

'Was that the Iraqis or the Iranians?' I asked, feeling stupid and scared.

Fielding frowned. 'Neither. It was Agent Yellow.'

'Agent Yellow as in James Bond Agent Yellow?'

Fielding did not respond to my sarcasm. Just as well. I didn't feel like a sparring match.

Chris said slowly, That was a ground effect. An earthquake. Explosions that small don't cause earthquakes.'

I shuddered. 'Explosions that small?'

Fielding looked grim. 'If our graphs are correct that was just a baby.'

I felt like grabbing someone and shaking them, felt like screaming or running out of there and never stopping. I managed to control the reaction with an effort, but it took me a while. In that time, Fielding went to the blackboard, picked up a piece of chalk and wrote: 2CaSO4 --> 2Ca20 + 2S + 203 X.

He underlined the X heavily.

'Listen up. School's in? Anyone understand this?'

Chris looked puzzled. I shook my head.

'What about this?' Fielding wiped some yellow dust from the blackboard beneath the original equation and wrote: 2CaCO3 --> 2Ca20 + 2CO X.

Chris said, '2CO' That's carbon monoxide?'

'Correct. These equations describe a reaction taking place in the local rock strata. Both reactions are impossible under normal conditions.' He tapped the board by the underlined X. 'Mister X here is a by-product of Agent Yellow. It catalyses an otherwise impossible reaction. The result is that sulphur is liberated from the local rock in crystal form. Lots of sulphur.'

'And the rock?'

'Becomes extremely unstable?' Fielding tapped the part of the equation that seemed to be composed of a worrying amount of oxygen symbols. A tiny puff of yellow powder leapt into the air; he waved it away. 'Explosive, in fact.'

Chris let out a breath: 'What about Mister X?. Where's it coming from?'

Fielding shrugged. 'As far as we can tell Mister X itself is one by-product of another impossible reaction. This one taking place within local biological matter.'

I went cold. 'You mean people?'

'People. Sheep. Plants. Anything biological. Anything with terrestrial DNA is being changed.'

I felt close to panic. 'I don't understand? We just came here to look for Noah's Ark. What are you trying to tell us?' Chris told me to shut up. 'I told you this was serious.' He switched his attention back to Fielding. 'You say terrestrial DNA is being changed. Into what?'

Fielding shrugged? 'We don't know. Think of the Ebola virus: seven molecules, three of them unknown. Millions of possible combinations.

Thousands of strains? Here we're dealing with thousands of molecules, only a few of them familiar to us. And the whole lot's changing - h.e.l.l, evolving - at a rate science tells us is impossible?'

I thought back to South Africa, to the hospital in Mulobizi. All those people bleeding out, becoming brain-dead sacks of infectious matter, becoming the actual virus itself. The woman we had found was bleeding out too - only she was bleeding acid.

'Well, where does this Agent Yellow come from? How do we stop it?'

Fielding wiped the blackboard with a rubber, erasing both equations with a single stroke, allowing another cloud of yellow dust into the air.

'The answer to both questions is: I have no idea. The only person who does is currently in isolation. Dying.'

The lab was located one level down, in a box-shaped structure held between the rear traction units? We walked down a narrow observation corridor until we came to a window. I stared through the thick gla.s.s into the isolation lab. The woman we had found lay on a metal table. She was still alive. The walls of the unit didn't quite block her screams.

With her in the lab were a number of suited technicians - one of them Imorkal. Their suits were connected by flexible plastic tunnels to the outside. The lab had its own environment - they were obviously taking no chances with contamination.