"Let's hope you're right," added Morpeth. "Once I bag those submarine-cruisers, I'll take my chance with the seaplanes." He rapped out an order to the quartermaster. Round swung Q 171 until she steadied on a course that would bring her once more within a short distance of the U-boat they had sighted soon after dawn. She was practically in the same position, but had swung with the change of tide--a fact which indicated that she was riding at anchor. For full half an hour Morpeth kept her under observation, but no sign of life was visible on board. "Another mutiny?" queried Meredith. "Hardly," replied Wakefield. "Unless it were a general mutiny amongst the submarine fleet, and this one were left behind. No, it's not that." "Then what do you think?" asked the Sub. "A booby-trap, possibly. If so, then Morpeth's stunt is off. I'll see what he says." The late skipper of M.L. 1071 went up to the R.N.R. officer and saluted--as he always did when on deck. "Yes," admitted "Tough Geordie" gloomily. "I'm afraid that it's a booby-trap. Those seaplanes, too, rather support the theory. And there are no signs of the submarine-cruisers. If nothing turns up by noon I'll torpedo that packet and leg it home at the rate of knots." "Any objection to my boarding her?" asked Wakefield. "None, as far as I am concerned," replied Morpeth, "provided, of course, you take all reasonable precautions. I'll be ready in case of an accident, but I must insist upon your taking a volunteer crew." A boarding-party was quickly forthcoming, consisting of Wakefield, Meredith, an armourer's mate, and two bluejackets. Launching the collapsible dinghy, they approached the U-boat, while Q 171, her concealed torpedo-tubes bearing on the former's hull, was ready to frustrate or at any rate to avenge any attempt upon the boarding-party. A rope ladder trailed forlornly over the U-boat's bulging side. This Wakefield studiously avoided, making for the after-part where the long tapering stern dipped beneath the surface. He hailed in German. No reply came from the apparently deserted craft, which was fretting at her cable in the now strong tideway. Wakefield motioned to the rowers to pull alongside. Followed by Meredith and the armourer's mate, he gained the rusty deck. "Hatches are closed," he said, in a low voice. "Soon have them open, sir," declared the petty officer confidently. "I think not," replied Wakefield. "Not until we've looked round a bit." The three men moved for'ard. There were signs that the boat had not recently been in commission. Apparently she had been towed out of harbour and moored in the isolated position off the Hoorn Reefs. Why? If as a mark-boat to assist returning submarines to verify their position, the fact of closed hatches was easily explained. Being shut, they enabled her to ride out a spell of bad weather, otherwise she would have foundered. "That's curious," exclaimed Meredith, pointing to the closed fore-hatch. "What?" asked Wakefield.