he did so, a train rumbled high above us.

With curiosity I followed the direction of his gaze, but what I saw conveyed to me nothing. About two feet above high-water mark a stout iron staple had been fixed into the concrete. To it was attached a piece of thin wire rope descending into the water, apparently used by the bridge workmen to moor their boats.

Having carefully examined the staple, Ray rowed round to the other three caissons, a few feet distant, but there discovered nothing. Afterwards, with my assistance, he pulled back to the Dalmeny side, where, at the base of one of the high square brick piers of the shore end of the bridge, the third from the land, he found a similar staple driven. Then we returned to the pier and crossed to North Queensferry.

My friend's next move was to enter the post office and there write upon a yellow form a telegram in German addressed to a person in Berlin. This he handed to the pleasant-faced Scotch postmistress, who, on seeing it in a strange language, regarded him quickly.

Ray remarked that he supposed she did not often transmit messages in German, whereupon she said:

"Oh, yes. The German waiter up at the Golf Club sends them sometimes."

"Is he the only German you have in North Queensferry?" he inquired casually.

"I've never heard of any other, sir," replied the good woman, and then we both wished her good-day and left.

Our next action was to climb the Ferry Hill at the back of the post office, passing the station and Carlingnose Fort, until we reached the club-house of the Dunfermline Golf Club, which commands a fine prospect over the wide estuary eastward.

No one appeared to be playing that morning, but on entering the club we were approached by a fair-headed, rather smart-looking German waiter. His age was about thirty, his fair moustache well trained, and his hair closely cropped.

I made inquiry for an imaginary person, and by that means was enabled to engage the man in conversation. Ray, on his part, remarked that he would be staying in the neighbourhood for some time, and requested a list of members and terms of membership. In response, the waiter fetched him a book of rules, which he placed in his pocket.

"Well?" I asked, as we descended the hill.

"To me," my friend remarked, "there is only one suspicious fact about that man—his nationality."

The afternoon we spent out at the naval offices, where I was introduced to the Superintendent and the second officer, and where I stood by while my friend again examined the big green-painted safe, closely investigating its lock with the aid of his magnifying glass. It was apparent that those in charge regarded him as a harmless crank, for so confident were they that no spy had been able to get at the plans that no night watch had ever been kept upon the place.

Through five consecutive nights, unknown to the caretaker, who slept so peacefully in his bungalow, we, however, kept a vigilant watch upon the place. But in vain. Whatever information our friends the Germans wanted they seemed to have already obtained.

Ray Raymond, however, continued to display that quiet, methodical patience born of enthusiasm.

"I'm confident that something is afoot, and that there are spies in the neighbourhood," he would say.

Nearly a fortnight we spent, sometimes in Edinburgh, and at others idling about North Queensferry in the guise of English tourists, for the Forth Bridge is still an attraction to the sightseer.

Upon the German waiter at the Golf Club Ray was keeping a watchful eye. He had discovered his name to be Heinrich Klauber, and that before his engagement there he had been a waiter in the basement café of the Hôtel de l'Europe, in Leicester Square, London.

His movements were in no way suspicious. He lived at a small cottage nearly opposite the post office at North Queensferry with a widow named Macdonald, and he had fallen in love with a rather pretty dark-eyed girl named Elsie Robinson, who lived with her father in the grey High Street of Inverkeithing. As far as my observations went—and it often fell to my lot to watch his movements while Ray was absent—the German was hardworking, thrifty, and a pattern of all the virtues.

One evening, however, a curious incident occurred.

Ray had run up to London, leaving me to watch the German's movements. Klauber had returned to Mrs. Macdonald's about eight, but not until nearly eleven did he come forth again, and then instead of taking his usual road to Inverkeithing to meet the girl Robinson, he ascended the hill and struck across the golf-course until he had gained its highest point, which overlooked the waters of the Forth towards the sea.

So suddenly did he halt that I was compelled to throw myself into a bunker some distance away to escape detection. Then, as I watched, I saw him take from his pocket and light a small acetylene lamp, apparently a bicycle-lamp, with a green glass. He then placed it in such a position on the grass that it could be seen from far across the waters, and lighting a cigarette, he waited.

The light on the Oxcars was flashing white and red, while from distant Inchkeith streamed a white brilliance at regular intervals. But the light of Heinrich Klauber was certainly a signal. To whom?

He remained there about half an hour, but whether he received any answering signal I know not.

Next night and the next I went to the same spot, but he failed to put in an appearance. Then, in order to report to Ray, I joined the morning train from Perth to London.

On arrival at New Stone Buildings I telephoned to Bruton Street, but Chapman, his valet, told me that his master had slept there only one night, had received a visit from a respectably dressed middle-aged woman, and had gone away—to an unknown destination. Therefore I waited for a whole week in anxiety and suspense, until one morning I received a wire from him, despatched from Kirkcaldy, urging me to join him at once at the Station Hotel in Perth.

Next morning at nine o'clock I was seated on the side of his bed, telling him of the incident of the lamp.

"Ah!" he exclaimed after a pause. "My surmises are slowly proving correct, Jack. You must buy a bicycle-lamp down in the town and a piece of green glass. To-night you must go there at the same hour and show a similar light. The matter seems far more serious than I first expected. The enemy is no doubt here, in our midst. Take this. It may be handy before long," and he took from his kit-bag a new .32 Colt revolver.

By this, I saw that he had resolved upon some bold stroke.

That evening, after an early dinner at the hotel, we took train to North Queensferry, and on alighting at the station he sent me up to the golf-links to show a light for half an hour; promising to meet me later at a certain point on the road to Rosyth.

I gained the lonely spot on the golf-course and duly showed the light. Then I hastened to rejoin my friend at the point he indicated, and found him awaiting me behind some bushes.

Almost at the moment we met, a female figure came along beneath the shadow of a high wall. She was a poorly dressed girl, but the instant she addressed my friend I recognised by her refined voice that it was Vera, the dainty daughter of the Admiral Superintendent.

"Elsie is waiting down by the Ferry Barns," she said quickly, in a low whisper, after greeting me. "Heinrich has not kept his appointment with her."

"You have the note?" he asked. "Recollect what I told you concerning the man Hartmann."

"Yes," she replied. Then, addressing me, she said, "Take care of these people Mr. Jacox. They are utterly unscrupulous"; and she again disappeared into the darkness.

Ray and I