a lifting fog, a calm sea, and the sun shining brightly overhead, all presaged a successful voyage. with the first pulsations of the motors derek's feelings of resentment towards the wagshot air station vanished. the bright, healthsome feeling of being afloat once more dispelled the hideous nightmare of damp concrete walls, hard beds, and inadequate food.

it soon became apparent that the task of towing the sea-plane was not so easy as derek imagined. the unwieldy machine—for out of its natural element it was unwieldy—yawed, dipped, and strained at the towing-hawser until derek ordered the second boat to make fast astern of the sea-plane and run at half throttle in order to steady the awkward tow.

with the ebb tide the passage through the "gateway" was soon completed. another ten miles would find the sea-plane and her tug out in the open sea.

in the tide-rip off fort churst the behaviour of the sea-plane gave rise to some anxiety, but, upon gaining the exposed waters of the english channel, the rate of progress was uniformly maintained.

presently derek noticed that a bank of fog was bearing down before a stiff southerly, or on-shore breeze. already the outlines of thorbury head, nine miles away, were blotted out, while, on the starboard hand, the long line of low, yellowish cliffs was cut up into sections by the rolling, fleecy vapour.

consulting the chart derek found that his course was due west magnetic, which would pass at least a mile to the south'ard of the dangerous headland. allowing for the reduced speed of the boats and the tow, he calculated that it would take about an hour to bring thorbury head broad on the beam.

down swept the fog, enveloping everything. from the steering-wheel it was almost impossible to distinguish the boat's stem-head; while astern the sea-plane was absolutely invisible.

at the end of forty minutes derek began to feel a bit doubtful of his position. miles astern he could hear the monotonous, mournful wail of the bodkin lighthouse. the sea, hitherto calm, was now setting in with a long roll, breaking heavily upon the invisible shore with a continuous, sullen roar.

"it seems rather shallow, sir," remarked the coxswain, as he shook the drops of moisture from the rim of his sou'wester. "shall i take a cast, sir?"

"yes, please."

in his anxiety about keeping the boat on her course derek had forgotten the indispensable lead-line. a cast gave two and a quarter fathoms, whereas, according to the chart, there ought to be a depth of nine.

"steer south-west," ordered derek. "there's something strange about this business," he added in an undertone.

"breakers ahead, sir!"

a partial lifting of the fog enabled the range of visibility to extend to nearly a quarter of a mile. as far as the eye could see the water was one seething mass of huge waves, from which there was no escape. the boats were trapped in the dangerous thorbury bay.

it was the result of an error of judgment on the part of derek daventry. he had laid off the course of the chart without taking into consideration the leeway made by the slowly-moving boats and the ungainly sea-plane; neither had he made allowance for the deviation of the compass, which happened to be one and a half points on a westerly course; there was also the indraught of the tide, which tended to set a vessel shorewards. all three factors were hard at work during the run through the fog-bank.

the first breaker bore down, enveloping the leading boat's bows in a swirling cascade of water. lifting the stocked anchor from its bed it swept the heavy mass of metal overboard. with a rush and a rattle the cable paid out until the boat brought up with a savage jerk. simultaneously she swung round broadside on to a particularly fearful-looking breaker. pouring over the cockpit the water promptly short-circuited the ignition, and the motor stopped dead. helpless in the trough of the sea, the boat was at the mercy of the next crested wave.

"cut away the sea-plane!" shouted derek.

a hand gave the tautened cable a slash with a knife. simultaneously the second boat cast off her steadying-line, and the abandoned sea-plane began drifting towards the shore with incredible rapidity.

to make matters worse the engineer, under the impression that the next sea would roll the boat completely over, kicked off his sea-boots and plunged overboard. in the grip of the tide he was swept to leeward, and even had he been an exceptionally good swimmer his chances of reaching the shore alive were very remote.

a deck-hand, seeing his comrade's predicament, jumped into the sea and struck out to his aid. it was a gallant but unavailing act, although by so doing he additionally hampered the work of rescue.

meanwhile the second boat, ignorant of what had occurred, was making heavy weather in the breakers. she had all her work cut out to keep "end-on" to the hissing, seething masses of water that threatened to overwhelm her. her coxswain-learner, who had a few months previously been steering a plough on a chalky wiltshire down, was handling the boat with cool and calculated skill.

for want of an engineer derek tackled the broken-down engine, working in feverish desperation in order to make an effort to save his two men. plugs were out and replaced in record time, the magneto was wiped and dried, and the cylinders "doped". a couple of determined swings of the cranking-lever and the engine fired, spasmodically at first, then with every indication of "carrying on".

"slip the cable!" shouted derek.

a couple of hands made their way along the heaving, slippery fore-deck, hanging on tenaciously as masses of solid water swept over them. watching his opportunity one of the men dropped down the fore-hatch, which his companion immediately replaced. in utter darkness, for the inspection lamp he carried was jerked violently against the coaming of the hatchway, the man toiled desperately, knocking out the stubborn pin of the shackle and allowing the cable to fly through the fair-lead.

the moment derek saw the end of the cable disappear beneath the waves he slipped in the clutch, while the coxswain steadied the vessel on her helm and bore down toward the two swimmers. by dispensation of providence the waves were no longer of such a threatening character. they were still formidable, and had to be treated with caution.

judging his distance well the helmsman brought the boat close alongside the now well-nigh exhausted men. already derek had thrown the clutch into neutral, and, losing way, the motor-boat stopped to windward of the swimmers. willing hands hauled them into safety, the engineer bleeding from a severe cut on the forehead, and showing distinct signs of light-headedness.

meanwhile the second boat, having drawn clear of the dangerous breakers, was returning to the aid of her consort. as she did so her motor "konked". instead of rendering assistance she was now in urgent need of help.

another partial lifting of the fog revealed the true position. within three hundred yards to the west'ard could be discerned the bold outlines of thorbury head, while to the nor'ard were the sand-dunes at the mouth of the shallow thorbury harbour, and it was between these two points that the breakers were raging. elsewhere the sea was almost as calm as the proverbial mill-pond, but in the mist derek had steered his boat right through the danger-zone.

heaving a line to the disabled motor-boat derek took her in tow, steering a circuitous course to avoid the now very apparent danger. then, having made a good offing, he handed the helm to the coxswain. the engineer was quite hors de combat. stripped of his saturated clothing and wrapped up in blankets, he was being attended to in the warm but cramped engine-room. still light-headed, he required the sole attentions of one of the crew to keep him under control.

derek was now able to review the situation. he felt far from comfortable on the matter. the seaplane was lost—probably smashed to matchwood on the beach. both boats were considerably knocked about, while two of the crew were out of action, and a third was temporarily disabled by reason of a badly-crushed finger-nail. in addition there was the loss of a practically brand-new anchor and forty fathoms of galvanized cable, two life-buoys, and a white ensign and its staff, which had been carried away during the towing manoeuvres.

and now, with malevolent irony, the sun was shining brightly, the last vestiges of fog had dispersed, and the sea was as smooth as glass.

visions of a court martial, or at least a stringent court of enquiry, stared derek in the face, with the possibility of being dismissed from the marine branch of the r.a.f.

"we'll be back just in time to miss the after-dinner parade, sir," remarked the coxswain, as the leading boat swept round the south-westerly extremity of sableridge and the pier opened out at less than two hundred yards distance. "it's close on three bells."

"there's not a man on the parade-ground," rejoined derek, "but there's a crowd on the pier-head, and all the boats are on their moorings 'cept the duty-boat. looks jolly funny."

but the mystery of suspended activity on the part of the marine depot was soon elucidated, for a stentorian voice called derek as his boat ran alongside the pier.

"cheerio, old bird! can you fancy yourself out of a job?"

derek had been doing so for the last hour.

"what's wrong?" he asked.

a dozen voices answered the question.

"armistice!"