'Nonsense!' said the official from the Admiralty.

Sir Walter got up and left the room while we looked blankly at the table. He came back in ten minutes with a long face. 'I have spoken to Alloa,' he said. 'Had him out of bed — very grumpy. He went straight home after Mulross's dinner.'

'But it's madness,' broke in General Winstanley. 'Do you mean to tell me that that man came here and sat beside me for the best part of half an hour and that I didn't detect the imposture? Alloa must be out of his mind.'

'Don't you see the cleverness of it?' I said. 'You were too interested in other things to have any eyes. You took Lord Alloa for granted. If it had been anybody else you might have looked more closely, but it was natural for him to be here, and that put you all to sleep.'

Then the Frenchman spoke, very slowly and in good English.

'The young man is right. His psychology is good. Our enemies have not been foolish!'

He bent his wise brows on the assembly.

'I will tell you a tale,' he said. 'It happened many years ago in Senegal. I was quartered in a remote station, and to pass the time used to go fishing for big barbel in the river. A little Arab mare used to carry my luncheon basket — one of the salted dun breed you got at Timbuctoo in the old days. Well, one morning I had good sport, and the mare was unaccountably restless. I could hear her whinnying and squealing and stamping her feet, and I kept soothing her with my voice while my mind was intent on fish. I could see her all the time, as I thought, out of a corner of my eye, tethered to a tree twenty yards away. After a couple of hours I began to think of food. I collected my fish in a tarpaulin bag, and moved down the stream towards the mare, trolling my line. When I got up to her I flung the tarpaulin on her back — '

He paused and looked round.

'It was the smell that gave me warning. I turned my head and found myself looking at a lion three feet off — An old man-eater, that was the terror of the village — What was left of the mare, a mass of blood and bones and hide, was behind him.'

'What happened?' I asked. I was enough of a hunter to know a true yarn when I heard it.

'I stuffed my fishing-rod into his jaws, and I had a pistol. Also my servants came presently with rifles. But he left his mark on me.' He held up a hand which lacked three fingers.

'Consider,' he said. 'The mare had been dead more than an hour, and the brute had been patiently watching me ever since. I never saw the kill, for I was accustomed to the mare's fretting, and I never marked her absence, for my consciousness of her was only of something tawny, and the lion filled that part. If I could blunder thus, gentlemen, in a land where men's senses are keen, why should we busy preoccupied urban folk not err also?'

Sir Walter nodded. No one was ready to gainsay him.

'But I don't see,' went on Winstanley. 'Their object was to get these dispositions without our knowing it. Now it only required one of us to mention to Alloa our meeting tonight for the whole fraud to be exposed.'

Sir Walter laughed dryly. 'The selection of Alloa shows their acumen. Which of us was likely to speak to him about tonight? Or was he likely to open the subject?'

I remembered the First Sea Lord's reputation for taciturnity and shortness of temper.

'The one thing that puzzles me,' said the General, 'is what good his visit here would do that spy fellow? He could not carry away several pages of figures and strange names in his head.'

'That is not difficult,' the Frenchman replied. 'A good spy is trained to have a photographic memory. Like your own Macaulay. You noticed he said nothing, but went through these papers again and again. I think we may assume that he has every detail stamped on his mind. When I was younger I could do the same trick.'

'Well, I suppose there is nothing for it but to change the plans,' said Sir Walter ruefully.

Whittaker was looking very glum. 'Did you tell Lord Alloa what has happened?' he asked. 'No? Well, I can't speak with absolute assurance, but I'm nearly certain we can't make any serious change unless we alter the geography of England.'

'Another thing must be said,' it was Royer who spoke. 'I talked freely when that man was here. I told something of the military plans of my Government. I was permitted to say so much. But that information would be worth many millions to our enemies. No, my friends, I see no other way. The man who came here and his confederates must be taken, and taken at once.'

'Good God,' I cried, 'and we have not a rag of a clue.'

'Besides,' said Whittaker, 'there is the post. By this time the news will be on its way.'

'No,' said the Frenchman. 'You do not understand the habits of the spy. He receives personally his reward, and he delivers personally his intelligence. We in France know something of the breed. There is still a chance, mes amis. These men must cross the sea, and there are ships to be searched and ports to be watched. Believe me, the need is desperate for both France and Britain.'

Royer's grave good sense seemed to pull us together. He was the man of action among fumblers. But I saw no hope in any face, and I felt none. Where among the fifty millions of these islands and within a dozen hours were we to lay hands on the three cleverest rogues in Europe?

Then suddenly I had an inspiration.

'Where is Scudder's book?' I cried to Sir Walter. 'Quick, man, I remember something in it.'

He unlocked the door of a bureau and gave it to me.

I found the place. 'Thirty-nine steps', I read, and again, 'Thirty-nine steps — I counted them — High tide 10.17 p.m.'

The Admiralty man was looking at me as if he thought I had gone mad.

'Don't you see it's a clue,' I shouted. 'Scudder knew where these fellows laired — he knew where they were going to leave the country, though he kept the name to himself. Tomorrow was the day, and it was some place where high tide was at 10.17.'

'They may have gone tonight,' someone said.

'Not they. They have their own snug secret way, and they won't be hurried. I know Germans, and they are mad about working to a plan. Where the devil can I get a book of Tide Tables?'

Whittaker brightened up. 'It's a chance,' he said. 'Let's go over to the Admiralty.'

We got into two of the waiting motor-cars — all but Sir Walter, who went off to Scotland Yard — to 'mobilize MacGillivray', so he said. We marched through empty corridors and big bare chambers where the charwomen were busy, till we reached a little room lined with books and maps. A resident clerk was unearthed, who presently fetched from the library the Admiralty Tide Tables. I sat at the desk and the others stood round, for somehow or other I had got charge of this expedition.

It was no good. There were hundreds of entries, and so far as I could see 10.17 might cover fifty places. We had to find some way of narrowing the possibilities.

I took my head in my hands and thought. There must be some way of reading this riddle. What did Scudder mean by steps? I thought of dock steps, but if he had meant that I didn't think he would have mentioned the number. It must be some place where there were several staircases, and one marked out from the others by having thirty-nine steps.

Then I had a sudden thought, and hunted up all the steamer sailings. There was no boat which left for the Continent at 10.17 p.m.

Why was high tide so important? If it was a harbour it must be some little place where the tide mattered, or else it was a heavy-draught boat. But there was no regular steamer sailing at that hour, and somehow I didn't think they would travel by a big boat from a regular harbour. So it must be some little harbour where the tide was important, or perhaps no harbour at all.

But if it was a little port I couldn't see what the steps signified. There were no sets of staircases on any harbour that I had ever seen. It must be some place which a particular staircase identified, and where the tide was full at 10.17. On the whole it seemed to me that the place must be a bit of open coast. But the staircases kept puzzling me.

Then I went back to wider considerations. Whereabouts would a man be likely to leave for Germany, a man in a hurry, who wanted a speedy and a secret passage? Not from any of the big harbours. And not from the Channel or the West Coast or Scotland, for, remember, he was starting from London. I measured the distance on the map, and tried to put myself in the enemy's shoes. I should try for Ostend or Antwerp or Rotterdam, and I should sail from somewhere on the East Coast between Cromer and Dover.

All this was very loose guessing, and I don't pretend it was ingenious or scientific. I wasn't any kind of Sherlock Holmes. But I have always fancied I had a kind of instinct about questions like this. I don't know if I can explain myself, but I used to use my brains as far as they went, and after they came to a blank wall I guessed, and I usually found my guesses pretty right.

So I set out all my conclusions on a bit of Admiralty paper. They ran like this:

Fairly Certain

(1) Place where there are several sets of stairs; one that matters distinguished by having thirty-nine steps.

(2) Full tide at 10.17 p.m. Leaving shore only possible at full tide.

(3) Steps not dock steps, and so place probably not harbour.

(4) No regular night steamer at 10.17. Means of transport must be tramp (unlikely), yacht, or fishing-boat.

Guessed

(1) Place not harbour but open coast.

(2) Boat small — trawler, yacht, or launch. (3) Place somewhere on East Coast between Cromer and Dover.

It struck me as odd that I should be sitting at that desk with a Cabinet Minister, a Field-Marshal, two high Government officials, and a French General watching me, while from the scribble of a dead man I was trying to drag a secret which meant life or death for us.

Sir Walter had joined us, and presently MacGillivray arrived. He had sent out instructions to watch the ports and railway stations for the three men whom I had described to Sir Walter. Not that he or anybody else thought that that would do much good.

'Here's the most I can make of it,' I said. 'We have got to find a place where there are several staircases down to the beach, one of which has thirty-nine steps. I think it's a piece of open coast with biggish cliffs, somewhere between the Wash and the Channel. Also it's a place where full tide is at 10.17 tomorrow night.'

Then an idea struck me. 'Is there no Inspector of Coastguards or some fellow like that who knows the East Coast?'

Whittaker said there was, and that he lived in Clapham. He went off in a car to fetch him, and the rest of us sat about the little room and talked of anything that came into our heads. I lit a pipe and went over the whole thing again till my brain grew weary.

About one in the morning the coastguard man arrived. He was a fine old fellow, with the look of a naval officer, and was desperately respectful to the company. I left the War Minister to cross-examine him, for I felt he would think it cheek in me to talk.

'We want you to tell us the places you know on the East Coast where there are cliffs, and where several sets of steps run down to the beach.'

He thought for a bit. 'What kind of steps do you mean, Sir? There are plenty of places with roads cut down through the cliffs, and most roads have a step or two in them. Or do you mean regular staircases — all steps, so to speak?'

Sir Arthur looked towards me. 'We mean regular staircases,' I said.

He reflected a minute or two. 'I don't know that I can think of any. Wait a second. There's a place in Norfolk — Brattlesham — beside a golf-course, where there are a couple of staircases, to let the gentlemen get a lost ball.'

'That's not it,' I said.

'Then there are plenty of Marine Parades, if that's what you mean. Every seaside resort has them.'

I shook my head. 'It's got to be more retired than that,' I said.

'Well, gentlemen, I can't think of anywhere else. Of course, there's the Ruff — '

'What's that?' I asked.

'The big chalk headland in Kent, close to Bradgate. It's got a lot of villas on the top, and some of the houses have staircases down to a private beach. It's a very high-toned sort of place, and the residents there like to keep by themselves.'

I tore open the Tide Tables and found Bradgate. High tide there was at 10.17 P.m. on the 15th of June.

'We're on the scent at last,' I cried excitedly. 'How can I find out what is the tide at the Ruff?'

'I can tell you that, Sir,' said the coastguard man. 'I once was lent a house there in this very month, and I used to go out at night to the deep-sea fishing. The tide's ten minutes before Bradgate.'

I closed the book and looked round at the company.

'If one of those staircases has thirty-nine steps we have solved the mystery, gentlemen,' I said. 'I want the loan of your car, Sir Walter, and a map of the roads. If Mr MacGillivray will spare me ten minutes, I think we can prepare something for tomorrow.'

It was ridiculous in me to take charge of the business like this, but they didn't seem to mind, and after all I had been in the show from the start. Besides, I was used to rough jobs, and these eminent gentlemen were too clever not to see it. It was General Royer who gave me my commission. 'I for one,' he said, 'am content to leave the matter in Mr Hannay's hands.'

By half-past three I was tearing past the moonlit hedgerows of Kent, with MacGillivray's best man on the seat beside me.