"'QKG--TOXZ--PJ'--code, thought so," muttered the Lieutenant-Commander, as he read the unintelligible message. "Mast-head signal astern, sir," reported Fordyce. The Hon. Derek swung round in an instant and levelled his binoculars at a pin-prick of yellow light. "Good!" he ejaculated. "That's what I was waiting for." CHAPTER XI Caught in the Net Presently the powerful night-glasses revealed the misty outlines of a large two-funnelled craft slowly making her way in a southerly direction, the while signalling steadily, pausing only to receive an answering message from one of the German patrols. Then, with all lights screened, came a pair of lean destroyers, zigzagging their way through the mine-field. After a while they steadied on their respective helms. Unless they altered course, they would pass at a distance not less than five cable-lengths from the lurking submarine. "One of their strafed raiders coming here to roost for a dead cert," quoth the Hon. Derek. "Hands to action-stations, Mr. Macquare. I mean to let that chap pilot me through the mine-field, and, with luck, I'll return evil for good by putting a torpedo into him." The two destroyers passed without sighting the British submarine. They were emitting dense columns of smoke that wafted over R19's deck as they steamed by. Two deductions were to be drawn from that circumstance. The boats were short of steam coal, which was a most cheerful bit of information. Also, from the fact that they were burning coal and not oil fuel, they were not by any means of the latest type of German torpedo craft. Presently the nearmost destroyer put her helm hard over and circled away from the submarine. Not until she was pointing in exactly the opposite direction to the one she had been following did she steady and slow down. Her consort still carried on until she had passed the approaching armed merchantman. Then she, too, flung about. Preceded and followed by her escort, the returning raider (for Stockdale's surmise was correct) steamed past at a rate of about five knots. It would have been a spendid opportunity for R19 to get home three torpedoes with mathematical precision, but reluctantly the Lieutenant-Commander stayed his hand. It was tantalizing but the greater issue was not to be lost sight of. Under electrical motive power, for it was too risky to make use of even the well-muffled internal-combustion engines, R19 fell in at the tail of the procession, keeping at a distance of four cable-lengths astern of the rearmost destroyer. Luck was in her favour, for not only was the night very dark, but the eddying clouds of smoke from the German vessels' funnels were frequently sweeping over the submarine, thus making a most effectual screen to her movements, while with her slow speed R19 did not show the "bone in her mouth"--the phosphorescent bow wave that at any high rate of speed would inevitably betray her position.