Five.

It had certainly been an extraordinary day-an extraordinary few days, I reflected, arriving back at the cot-house on the motorcycle. And what had happened to spring? I lit a fire to drive off the effects of the sea mistvalley fog and made myself a corned beef sandwich. Later that night there was a knock on the cot-house door. It was Ryman, and he began by begging for a drop of drink like a Glasgow tramp, though not exactly in the manner of one.

"Would you by any chance have any alcohol in the house? Something has happened again which must make me break my ordinance of self-denial."

I settled him down with a whisky in the most comfortable chair I could find. He stared at the floor for a long time.

"Gill has gone," he muttered finally.

"I know. I pa.s.sed her in Mackellar's trap. I'm surprised you didn't take her in the car, given her condition."

"You know that too, then. Petrol ration. We've run out."

"I could have got some from Dunoon for you."

A look of misery pa.s.sed over his face. "This is her seventh pregnancy, Henry. All the others have resulted in miscarriages."

Something landed on the slates above us-a rook? a windblown branch?-but it was as if the very sky had cracked. He began speaking quickly. All that was interior came into the open air. "We always wanted a child. She's thirty-five now; she'll try again next year, too, if this one does not survive. She says it's her duty and she will not shirk from it. That is why she has gone south."

"To the Isle of Wight." I said.

"Yes. As you know, the Blackfords, her family, live there. They usually nurse her afterwards. The miscarriages are happening earlier and earlier, so she has gone down in good time, in expectation of the worst."

"Perhaps it will be different this time."

"I doubt it. It is a matter of faith alone for us now. There is clearly some scientific reason for what has been happening. It is do with blood and how it is structured into different groups. The rhesus factor, which you know about. A very new area of study. So...we have sent samples of our blood to that man Julius Brecher, whom you mentioned."

"And mine, too, I hear," I said.

Ryman looked sheepish. "Ah, yes. Sorry about that. It was Gill's idea to do it like that. She reads a lot of novels. I myself would have asked you directly. The point is, we thought..."

His voice trailed off. I put another log on the fire and waited for him to continue, which in due course he did. "The point is that we hoped, if it happened again, if the baby died, you might, er, stand in. We wanted to get your blood tested for the purpose."

"Stand in for a baby?" For one bizarre moment I thought they meant to adopt me.

"What? No. We mean, we wondered...if you would...with Gill. We wondered whether would you...with my wife, in order that she might conceive a child? If it all goes wrong this time, I don't think either of us could go through it again. So...well, we have at least established your blood is not contradictory. Mine is, you see."

Shocked, I took a large gulp of whisky and stood up to pat my pockets nervously, searching for cigarettes.

"That's very bad for your health," observed Ryman from his seat, watching me light up once I had found them.

I gave a burst of laughter at this. He gave me a hurt and angry look and rose to his feet himself.

"I'm glad you find this all so amusing," he said, facing me.

"Wait." I put a hand on his shoulder. "I just thought it was funny that you should be thinking about my health at a time like this. I meant nothing by it."

He sat down again, sniffing. "I see. Well, it's natural that the mind should seek refuge at times of distress in its most familiar habits, and one of mine is to tell people when they are doing things that are bad for them."

Then it was his turn to laugh, bitterly. "There I go again. Gill says I am always doing this. a.n.a.lysing future outcomes. She thinks it is because my mind's always working so hard that we are not able to have children. As if my whole body were taken up with thinking."

Tears ran down his cheeks as he spoke.

"That's nonsense, sir," I said, as kindly as I could manage.

He took out a handkerchief and blew his nose, smiled weakly at me, then abruptly stood up again and left.

Six.

I spent the night in turmoil. In the morning, further to discomfit me, as it seemed, the Junkers rumbled over again. So much had taken place that I had almost forgotten about it. I jumped out of bed just in time to watch it whoosh over my head, the cameras on its wingtips clearly visible this time. The rest of the day was spent drawing charts-not because I was mindful of Whybrow's incontinent warning but because I had to take my mind off everything that had happened-in particular the thought of poor Gill and the baby, and Ryman's peculiar request. The two seemed in no way commensurate. spent the night in turmoil. In the morning, further to discomfit me, as it seemed, the Junkers rumbled over again. So much had taken place that I had almost forgotten about it. I jumped out of bed just in time to watch it whoosh over my head, the cameras on its wingtips clearly visible this time. The rest of the day was spent drawing charts-not because I was mindful of Whybrow's incontinent warning but because I had to take my mind off everything that had happened-in particular the thought of poor Gill and the baby, and Ryman's peculiar request. The two seemed in no way commensurate.

There was no sign of the Prophet and, not wishing to confront in my mind his outlandish suggestion, I didn't seek him out. The whole affair was quite beyond me. There was, in particular, something ghoulish about the idea of arranging, even if provisionally, to put another child in a woman's belly when the one that was already there was not yet dead. It would take great mental and emotional detachment to do that, I thought. Detachment or desperation.

Without stopping for lunch I got my head down again until I was up to date with my work. Whybrow could stuff it all down his gullet for all I cared, but I didn't want him denigrating me to Sir Peter.

I made supper. Potatoes and carrots on the stove, a mackerel Providence had reserved for me at the end of Mackellar's lines. Plus a bottle of beer, and a cigarette for pudding. It was only then, in a tobacco trance, that I conceived of a simple plan to strike back at the German plane using a series of cracker balloons.

I seized upon the notion with dangerous fervour. Now that I look back at this stupid idea, I realise its emotional impetus may have come from Whybrow's implication that I had been neglectful in not helping those people who had rowed across the Clyde following the bombing of the factory in Greenock; and, of course, from wishing to displace from my mind the business with Gill and the baby. The role of displacement is, it seems to me, just as important in consciousness as it is in the environment, though whether something similar to the distributive working of turbulence takes place in the brain I could not say.

Whatever its mental roots, the practical conception for the plan was derived from the not dissimilar Free Balloon Barrage that I had worked on in my early career at the Met Office. Because the government had ordained it, I didn't think the idea stupid at the time. Now, of course, older and marginally wiser, I would take the fact that the government had ordained it as a fair indication of its likely stupidity.

As to the plan itself-each balloon could be primed to go off at a different height. If I set them up right, perhaps in a line behind the beech tree walk, and detonated them at the correct periods, I might be able to create a barrier into which the Junkers would fly and damage itself. For added nuisance value, the length of the copper-wire aerials beneath the balloons could be increased, in the hope that one of them might get caught up in the plane's propellers. It would all require precise timing-and a lot of balloons.

I broke open all of my crates and worked late into the night, filling balloon after balloon. I used up my whole supply of hydrogen materials, then settled down to sleep with all the balloons nestled around the bed. No smoking now: I'd weighted them all with small sealed cartons of motorcycle oil, mixed with a little petrol. For extra explosiveness, I attached a collar of magnesium to the cartons, which were themselves connected by fuse to the main cracker charge.

I had no idea if my plan would work, but it was surely worth a shot. Calculating the likelihood of one of the balloons actually being hit by the plane was impossible. There were too many variables.

But there could be no harm in trying. That is what I thought, at any rate. Underneath the thought, however, was the vision of a brilliant spectacle, something that would rescue my part in the war and be talked about for generations to come.

Seven.

In the light of day, I felt a twinge of unease about what I was planning. I worried about the waste of materials and the trouble I would get into if it didn't work. Or, indeed, if it did work. But by then, with no clear idea of the significance it would have, I was already committed to the idea. I went to the beech tree walk to set a series of tether switches to which each of the balloons could be attached, enabling them to be released in sequence. I then came back carrying one balloon at a time, each weighted with extra incendiary materials and trailing an extra-long copper-wire tail.

It was quite hard to put all this in place, as a high wind was blowing and each balloon had to be tethered with its burden and tail neatly laid out, to avoid tangles. The tether switches were strings attached to a fuse and a ground-pin, like a tent-pole-I had rigged it up so that each fuse would ignite its neighbour.

I did not finish until eleven, when who should appear but Ryman, walking along the opposite bank of a stream that ran under the beeches. He was wearing corduroy trousers and a thick woollen sweater and carrying a bottle of milk. I quickly crossed over.

"What are you doing?" he asked, eyeing the bundle of leftover tether packets under my arm.

"Oh, this and that," I said casually, which was not perhaps the best way of deflecting attention from my activities. "I have been thinking about what you said the other evening," I said tactically, in order to distract him.

His response was to look as if he were having a thought: one thought after another, in fact. Then he repeated, "What exactly are you doing?"

"I'm laying a sequence of cracker balloons." At any moment he might have walked through the long line of red balloons on the other side of the beeches, so I thought it best to tell him a little of the truth.

"What are you you doing with that milk?" I said as another diversionary measure. doing with that milk?" I said as another diversionary measure.

"Come," he said. "I'll show you."

We walked alongside the stream, towards the wooden footbridge. The whole place was filled with green mossy light and the smell of vegetation. Inside the glade, where the wind had less effect, the midges were greatly in evidence, and I was soon slapping and itching. The sense of peace and composure I'd felt in that place was no longer in evidence. Quite the reverse.

As we leaned over the bridge, which sagged slightly under our weight, Ryman began pouring milk from the bottle into the running, turning water, making a cloudy vortex on one side of a rock and a white-lined plume on the other.

He chanted a ditty as he poured. "Big whirls have little whirls that feed on their velocity. Little whirls have lesser whirls and so on to viscosity-in the molecular sense." He paused, before continuing in his ordinary voice, "And this is the gospel of the Lord."

I watched him pour more milk into the stream, where it turned in the opalescent eddy of itself, before being swept away by the surrounding water.

"Or it might not be the gospel. Unfortunately, we cannot see the whole picture, and must carry on our business on premises that are still in the hands of the builders. That business is the search."

His mixing of both milk and metaphor apparently over for the time being, he paused again before looking at me very directly. "I think you, too, Henry, have been searching for some kind of answer." Below us, the water riddled through the stones. "How to use my so-called number in war is what you're after, I suppose?"

I gave a disconsolate nod of confirmation.

"Who sent you?"

It was pointless to try to cover up any more. "Sir Peter Vaward."

"You've really been spying on me, all this time?"

"Not very successfully."

He put his fingers to his brow. "I had an idea from the first it might be something like that. You do make things complicated for yourself. Why didn't you just ask me?"

"It's war work," I said vacuously. "I was afraid you might have conscientious objections. And anyway, I did ask you, several times."

The Prophet shrugged. "Sir Peter Vaward, eh? One of the gas men at Porton Down, he used to be, before he got so grand...He used some of my equations to find out how quickly poison gas would disperse." Peter Vaward, eh? One of the gas men at Porton Down, he used to be, before he got so grand...He used some of my equations to find out how quickly poison gas would disperse."

"He's just trying to do his job. The Met Office needs to comprehend turbulence in a single coherent scheme. The truth is, they need it especially for the landings on mainland Europe."

"I know what those will mean," Ryman said sternly. "I know what killing is."

I saw the Prophet in the cruel delirium of the trenches, half mad with horror, the crazy Albert Hall vision rising as if on scaffolding out of that mess of dead men and horses, only to be lost under a pile of coal.

"But you'll tell me?" I pleaded. "Even if it goes against your principles?"

"The practical application of science is an individual's moral choice. The theory itself is neither moral nor immoral. See here, for goodness' sake!"

As if he were watering a flowerbed, he poured the last of the milk into the stream, where-though not exactly-it swirled round as before, until its behaviour became unsteady, particles of milk and water enmeshing in little puffs of diluting white as they flowed over rocks and through weed.

Ryman spoke with an air of authority-although it was the authority of a man unburdening himself. "Weather energy goes round in circles, runs down corridors, cascades down stairways. It diffuses, regathers, reforms, diffuses again. It moves in jets and trickles, is divided by layers thick and thin-layers that themselves can be throughways as well as shields. It's always moving through one system to another, taking different shapes over time. That's why there'll always be the unexpected. The number will not help you solve that problem directly."

He paused to grip the rail of the bridge before resuming speaking more quickly, with a brighter timbre to his voice. "But if you want help with your war, I will give you some peaceful advice. The extent of unexpectedness can be modified, increasing the probability of prediction. You must focus on the layers and boundaries between weather systems to draw out that predictability. Each layer has a different predictability. You must concentrate on the barriers between these differently characterised flows. The width of the flows is key, but also their depth, and how long they last. So the s.p.a.cing-in time and geographically-of where you make your observations therefore becomes crucial. Don't think of the date for your invasion, or you will make a prison for yourself. Think of your data instead. How does it fit into the surrounding context?"

I slapped my neck. Was he really just saying we had to measure better? If he was, it was a preposterous thing to offer up as the secret of weather forecasting. I felt like pushing him off the side of the bridge, into the water.

I lit a cigarette to counter the midges-and to give me the courage to speak my mind. "What Hitler is doing is wrong. Morally wrong. Surely you must see that. If you really cared about avoiding murder and death you would help me."

"Very well." He pointed at the stream with the empty milk bottle. "Look. There is no milk there now. The important thing to remember is that, in itself, turbulence decays, until it is regenerated by new energy sets. This is where questions of range and context come in. Barrier questions, boundary matters, timing issues. Beginnings, middles and ends. These are the important things. These are the limits which affect the predictability of different atmospheric layers. You need to find the so-called Ryman number for each part of the story. The problem is, it has already changed by the time you come to the next part. The time meter is always ticking as you move about spatially. More or less everything comes down to that basic relation."

I guess this was the moment of revelation, though it didn't seem like a revelatory experience. I felt unsatisfied. The knowledge I was after was, if anything, more elusive than ever. Perhaps I was foolish to have expected that the answers could just come like logs down a chute. Yet I clearly owed him for something.

I took his hand and shook it. "Thank you. I think I understand better now. But I do have some other questions."

He looked at me coolly, as if I was pushing my luck. "Go on."

Everything I'd been thinking about came out in a rush. "To invade a piece of France or Belgium, how much of the adjoining coast would we have to do the forecast for? How long before the invasion day should the critical forecast take place? How far beyond the immediate vicinity, one or other part of the Channel, should weather systems evolving from elsewhere be considered?"

"Oh for goodness' sake," he said, raising his eyebrows. "The edge is always dangerous. You must try to track all all the limits, the limits, all all the barriers. That is what I've been trying to drive home to you. Remember this, too: that a barrier between two weather patterns might also be a narrow corridor for a third. Watch out for what's flying down that narrow corridor, Henry. That can change everything for miles around." the barriers. That is what I've been trying to drive home to you. Remember this, too: that a barrier between two weather patterns might also be a narrow corridor for a third. Watch out for what's flying down that narrow corridor, Henry. That can change everything for miles around."

"But I don't know how to make these distinctions! I have a fifty-mile stretch of beach and I am not sure where your beginnings, middles and ends of the various weather systems fall on it."

He sighed. "You just must use your common sense, taking care how you relate the different zones. Where you cannot measure, you must sensibly approximate. Use randomisation judiciously."

I seemed to hear something by the back of my head. Something very distant and apparently insignificant but in fact prodigiously imperilling. But I did not understand what it was, at least I didn't right then. I thought it was a midge, maybe, or some whining mechanical process taking place in the hills or on water. The Cowal in wartime was full of such noises.

His voice warmed a little. "Don't pretend to the military that it can all be computed, Henry. It can't. Not yet. We don't have the brain power. Not even if every member of every Allied met office sat side by side doing one tiny part of the calculation each, as in my Albert Hall fantasy. We need machines to do it."

With that he turned away, as if to head for home, before turning back and looking at me directly, face to face where we stood on the bridge. "I notice you haven't asked me about Gill. You will think about the matter we spoke of?"

I nodded, uncertain as he departed as to what kind of contract, if any, I had just made-but that, as things turned out, was the least of my troubles.

Eight.

As I watched Ryman's tall figure stride across the field, I realised what it was, that half-familiar noise I'd been hearing. It was the German plane, coming in low. That is what I had heard. We both turned to look. Without stopping to think, I ran as fast as I could to the start of the beech tree walk, where I had set the first of my release switches.

The Junkers came over, already in the curve, readying itself to turn. They could have shot Ryman by now, had they wanted. Perhaps they really were just taking pictures...