"It's impossible," said Winstanley. "I sat next to him for nearly half an hour."

"That's what's so clever," I said. "You were too interested in other things to look at him closely. You knew that he might be well enough to come tonight and, as First Sea Lord, it was natural for him to be here. Why should you suspect that it wasn't him?"

Sir Walter got up and left the room. He came back after ten minutes. "I've spoken to Alloa. I got him out of bed -- he was very angry. He hasn't left his house all day."

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

"This young man is right. He understands our enemies. People only see what they expect to see. This man came late, spoke little, and left early but he behaved exactly as we would expect Lord Alloa to behave."

"But I don't understand," said Winstanley. "Our enemies don't want us to know what they have learnt about our war plans. But if one us talked to Alloa abut tonight's meeting, we would discover immediately that he hadn't been here."

Sir Walter laughed angrily. "That shows their cleverness again, in choosing Alloa. They took a risk, but everybody knows that Alloa is a sick man and is often too ill to go to meetings. And even when he is well, he is impatient, difficult, and a man of very few words. Which of us was likely to speak to him about tonight?"

"But the spy hasn't taken the plans," said Winstanley. "He saw them, but could he carry away pages of information in his head?"

"It's not difficult," said the Frenchman. "A good spy can remember things photographically."

"Well, I suppose we'll have to change our plans," said Sir Walter unhappily.

"There's another problem," said Royer. "I said a lot about the plans of the French army. That information will be very valuable to our enemies. That man, and his friends, must be stopped immediately."

"They could simply send their information in a letter," said Whittaker. "It may already be in the post."

"No," said Rower. "A spy brings home his information personally and he collects his pay personally. These men must cross the sea, so we still have a chance. You must watch the coast and search ships. It is desperately important for both France and Britain."

Royer was right. We could do something. But none of us felt very hopeful. How, among the forty million people in Britain, could we find the three cleverest criminals in Europe?

I found the place. "Thirty-nine steps," I read, and again, "Thirty-nine steps -- I counted them -- high tide,10:17 p. m."

It was no good. There were more than fifty places where high tide was at 10. 27. We needed more information than that.

"Not them. They have their own secret way, and why should they hurry? They don't know that we're after them. Where can I get a book of Tide Tables?"

Sir Walter went off to Scotland Yard to get MacGilllvray. The rest of us drove to the Navy Offices where we went to a big room full of books and maps. We got a copy of the Tide Tables, and I sat down and looked through it while the others watched.

He gave it to me.

"Don't you see it's a clue?" I cried. "Scudder knew where they were going to leave England. Tomorrow was the day, and it's somewhere where high tide is at 10:17."

Whittaker clearly thought I had gone mad.

"Where is Scudder's book?" I asked Sir Walter. "Quick, I remember something in it."

Then, suddenly, I had an idea.

"Perhaps they've already gone tonight," someone suggested.

Whittaker looked happier. "It's a chance," he said. "Let's go to the Navy Offices."

I thought hard. What did Scudder mean by steps, and why was it so important to count them? It must be somewhere with several paths going down to the sea. This path would be the only one with thirty-nine steps.

Why was high tide important? In a big harbour the tide doesn't matter. It is only important in a small harbour, or somewhere where there is no harbour at all.

I wrote out my ideas on a piece of paper:

I had another thought and checked the time of regular ships leaving England. There was no ship at 10. 17.

I am not Sherlock Holmes. But I am used to using my head, and when I guess, my guesses are often right.

Then I thought about where a man would leave England if he were going to Germany. Not from the south coast, or the west coast, or Scotland. It would be somewhere on the east coast, probably between Cromer and Dover.

(1) A place where there are several paths down to the sea. One of these has thirty-nine steps.

ALMOST CERTAIN

(2) High tide at 10. 17p. m. A place where it is only possible for a ship to leave the coast at high tide.

(3) Probably not a harbour, but open coast with cliffs and a beach.

(4) Ship probably a small one, a yacht or a fishing boat.

Sir Walter and MacGillivray arrived. They had men watching all the harbours and railway stations with descriptions of the three men. But none of us thought that this would help

It seemed strange to be sitting at a table, watched by a groupof very important people, trying to understand something written by a dead man. But it was a matter of life or death to us.

(5) Somewhere on the east coast between Cromer and Dover.

"Here's the best I can do," I said. "We have to find a place where there is a path with thirty-nine steps down to a beach. It must be somewhere on the east coast. Of course, it's somewhere where high tide is at 10. 17 tomorrow night. Who can we ask who knows the east coast really well?"

Whittaker said he knew a man who lived in south London. He went off in a car to get him and came back at about one o'clock in the morning with an old sailor who had worked all his life on the east coast.

"Well, I don't know. Of course, there's the Ruff --"

"What's that?"

"No, that's not private enough," I said.

"We want you to tell us about places you know on the east coast where there are cliffs and steps going down to the beach," said Winstanley.

"This looks hopeful," I cried. "How can I find out when high tide is at the Ruff?"

"If one of those paths has thirty-nine steps, then I think we have a good chance," I said. "Can I take a car, Sir Walter, and a map? If Mr MacGillivray can help me, perhaps we can prepare something for tomorrow."

I opened the Tide Tables at Bradgate. High tide was at 10. 27 on the 15th of June.

He thought for a minute or two. "There are a lot of seaside towns -- holiday places -- where there are steps from the town down to the beach."

"It's in Kent, near Bradgate. There are cliffs with houses along the top -- big houses. Some of the houses have steps down to a beach Mostly rich people live there, the sort of people who like to be private."

I closed the book and looked up at the others.

"I can tell you that, sir," said the sailor. "I used to go fishing there. High tide is ten minutes before Bradgate."

It seemed strange for me to take control like this. But I was used to action, and they could see it. It was the Frenchman, Royer, who said what they were all thinking. "I am quite happy," he said, "to leave this business in Mr Hannay's hands."

At half-past three in the morning I was driving through Kent in the moonlight, with MacGillivray next to me.