His memory had flashed back to the notice he had read, offering a reward in connection with certain paint marks on the Forth Bridge. No doubt the misguided "person or persons" who had daubed the bridge had used luminous paint. This, of course, would explain the phosphorescent glow which had so puzzled him. The question now was, had it been done merely as a joke or for some specific object? If for a joke, it was difficult to see where the humour came in; if for an object, it was equally difficult to see what purpose it could serve. "I'll have a closer look at the bridge when I've rested a bit," he told himself. That afternoon the Lieutenant took a train to Queensferry. He then set out to walk back over the bridge along the railway track. The paint daubs were clearly visible, though not, of course, phosphorescent in the daylight. It struck him as peculiar that these marks had a definite shape, or rather two definite shapes. One took the form of a St. Andrew's Cross, the other the form of a star--that is, instead of two intersecting lines of the same length, there were four. But that was not all. A careful examination showed that these stars were placed at the weakest part of the bridge; in other words the parts which would be easiest to destroy by means of dynamite. Finally, the marks could only be seen from above the bridge, not from below it. Lawless whistled softly when he had made these discoveries. He returned to the depot, and went at once to his commanding officer and told him of the discoveries he had made. He also explained at some length his own theory concerning them. The commanding officer listened patiently at first because he was a good-natured fellow and liked to see his officers exercise initiative and resource. But his interest in the story soon flagged, and when Lawless began to state his deductions it wilted entirely. An expression of resigned boredom appeared on the officer's face and remained there till the interview came to an end. "So you see," concluded the Lieutenant eagerly, "it requires no great effort of imagination to realise what the German plans are." But it required more imagination than the commanding officer was capable of exercising. Indeed, he was not an imaginative man and prided himself upon the fact. He didn't regard imagination as consistent with the duties of a soldier; consequently, he made no effort to encourage it in those under his command. "It's a very ingenious theory, very!" he said; "but unfortunately the grounds upon which you base it appear to me to be entirely unsatisfactory." And for the time being that settled the matter so far as the commanding officer was concerned. That evening, when the Lieutenant arrived at the hangar preparatory to setting out on the nightly scouting expedition, he brought with him a curious looking implement. It consisted of a stout spar about ten feet long, at the end of which was attached a long, curved knife, not unlike a billhook in appearance.