The three men listened intently. The faintest alteration in the rhythmic purr of the U-boat's engines set their nerves on edge. They knew something of the fearfully ingenious devices used to strafe Hun submarines, and now they were metaphorically at the business end of a big gun, whereas formerly they had been behind it. It was a disconcerting affair, exposed to unseen perils that might without warning send them to their death in company with a crowd of Huns. And, unless Pyecroft had succeeded in getting safely ashore, the manner of their going would remain a secret for all time. For several long-drawn seconds the trio listened in silence. They knew by the difference in the pulsations of the motors that the U-boat had been running on the surface. The diving-tanks had not been filled, otherwise they would have heard the gurgling inrush of water. For some reason the submarine had brought up and was drifting with wind and tide. A quarter of an hour elapsed, then the petrol-motors were restarted. Very soon after the door of their cell was unlocked and a couple of Hun seamen appeared. "Come you on deck!" one exclaimed, with such a broad smile that Cumberleigh and Co. suspected a dirty trick on the part of Fritz. "Anything to get a breather," ejaculated Blenkinson. "Lead on, old bird!" In single file the three British officers followed their guide along the intricate alley-way and on deck via the conning-tower hatchway. A hurried glance gave no clue to the unexpected change of environment. The U-boat was forging ahead. By noting the position of the sun the captive officers knew that the course was approximately east, and that direction led towards Germany. The skyline was unbroken. Neither the proximity of land nor the presence of another craft was evident to account for the change of attitude on the part of their captors. "We friends is," continued the Hun who had previously addressed them; and as evidence of good faith he handed the Englishmen a box of cigarettes. The dearth of tobacco, cigars and cigarettes that had been noticeable amongst the ratings during von Preugfeld's regime was now, temporarily at least, a thing of the past. The former ober-leutnant's cabin had been systematically ransacked, with the result that a goodly store of tobacco had been discovered and distributed. "What has gone wrong?" inquired Captain Cumberleigh, speaking slowly in order to make himself understood. "Where are your officers?" The seaman paused before replying. In order to ingratiate himself he would not have hesitated to confess that the Prussian tyrants had been thrown overboard; but in the event of the submarine making Hamburg safely or else being overhauled by a vessel flying the Black Cross Ensign, the knowledge that the Englishmen knew the secret might prove decidedly awkward.