“Of course,” Furley observed, “ciphers can lead you—­”

He stopped short.  Julian, who had been leaning over towards the cigarette bog, glanced around at his friend.  There was a frown on Furley’s forehead.  He withdrew his pipe from between his teeth.

“What did you say you made of it?” he demanded.

“`Thirty-eight steeple on barn.’”

“Thirty-eight!  That’s queer!”

“Why is it queer?”

There was a moment’s silence.  Furley glanced at the little clock upon the mantelpiece.  It was five and twenty minutes past nine.

“I don’t know whether you have ever heard, Julian,” he said, “that our enemies on the other side of the North Sea are supposed to have divided the whole of the eastern coast of Great Britain into small, rectangular districts, each about a couple of miles square.  One of our secret service chaps got hold of a map some time ago.”

“No, I never heard this,” Julian acknowledged.  “Well?”

“It’s only a coincidence, of course,” Furley went on, “but number thirty-eight happens to be the two-mile block of seacoast of which this cottage is just about the centre.  It stretches to Cley on one side and Salthouse on the other, and inland as far as Dutchman’s Common.  I am not suggesting that there is any real connection between your cable and this fact, but that you should mention it at this particular moment—­well, as I said, it’s a coincidence.”

“Why?”

Furley had risen to his feet.  He threw open the door and listened for a moment in the passage.  When he came back he was carrying some oilskins.

“Julian,” he said, “I know you area bit of a cynic about espionage and that sort of thing.  Of course, there has been a terrible lot of exaggeration, and heaps of fellows go gassing about secret service jobs, all the way up the coast from here to Scotland, who haven’t the least idea what the thing means.  But there is a little bit of it done, and in my humble way they find me an occasional job or two down here.  I won’t say that anything ever comes of our efforts—­we’re rather like the special constables of the secret service—­but just occasionally we come across something suspicious.”

“So that’s why you’re going out again to-night, is it?”

Furley nodded.

“This is my last night.  I am off up to town on Monday and sha’n’t be able to get down again this season.”

“Had any adventures?”

“Not the ghost of one.  I don’t mind admitting that I’ve had a good many wettings and a few scares on that stretch of marshland, but I’ve never seen or heard anything yet to send in a report about.  It just happens, though, that to-night there’s a special vigilance whip out.”

“What does that mean?” Julian enquired curiously.

“Something supposed to be up,” was the dubious reply.  “We’ve a very imaginative chief, I might tell you.”

“But what sort of thing could happen?” Julian persisted.  “What are you out to prevent, anyway?”