"Hear that noise? Sounds like an aeroplane overhead," exclaimed Branscombe.

It was high noon. The Donibristle was approximately five hundred miles nor'-west of the Sandwich Islands. The sky was clear and bright. Air and sea were shimmering under the powerful rays of the sun.

"Hanged if I can," replied Burgoyne, "I think you're mistaken, old son. It's hardly likely that a seaplane would be buzzing round over this part of the Pacific."

Nevertheless he craned his neck and gazed at the blue vault overhead. The two chums, off duty, were standing aft. Close to them Messrs. Tarrant and Miles were engaged in a heated argument over the merits and demerits of the products of a certain firm of tabloid drug manufacturers. Colonel and Mrs. Vivian were seated in canopied deck-chairs under the lee of one of the deck-houses. Captain Blair and the Chief Engineer were pacing to and fro on the starboard side of the deck, earnestly discussing a technical point in connection with the distilling plant. Hilda Vivian happened to be "listening in" in the wireless cabin, hearing vague sounds which Peter Mostyn assured her were time signals from a shore station on the Californian coast.

"What's that," sang out Tarrant, overhearing the Third Officer's remark. "Aeroplane—what?"

Presently at least a dozen pairs of eyes were scanning the sky, but without success.

"Can you hear it now?" asked Burgoyne.

"No, I can't," replied Branscombe bluntly, "but I swear I did just now."

"Would it be the dynamos you heard?" inquired Angus.

"No; aerial motor," declared the Fourth Officer firmly. "In fact," he added, "I believe I can hear it now."

"Ye maun hae a guid pair o' lugs," observed Angus caustically.

Branscombe said nothing more, but hurried on to the bridge. An inquiry of the Fifth Officer and the two quartermasters resulted in a negative reply. Nothing had been seen or heard of an aircraft of any description.

"Good job I didn't bet on it," remarked Philip, when he returned and reported the result of his inquiries. "But no one can prove I didn't hear it," he added, with a marked reluctance to admit defeat.

"I certainly heard a buzz right overhead," announced Colonel Vivian. "I rather pride myself on my hearing, but I'm hanged if I saw anything. Besides, if there were a seaplane so far out from land, wouldn't it have come down to within a few hundred feet and had a look at us?"

"I haven't seen an aeroplane for months," said Withers plaintively. "At one time, when I was running from Southampton to Cherbourg and Havre during the war, the sky was stiff with 'em. Hardly ever bothered to look up at the things. Now they're becoming novelties again. It would seem like old times to see a Handley-Page again."

Meanwhile Mostyn was continuing to give practical lessons to Hilda Vivian.

"What an extraordinary noise," exclaimed the girl, removing the receivers from her ears. "Much fainter than before."

Mostyn took up the ear-pieces. There was a call, but in a different wave-length. He was "standing-by" on the 600-metre wave. Rapidly adjusting the "Billi" condenser he failed to attain the desired result. Apparently the sending-out apparatus was of a totally different tune. That discovery puzzled him, since almost every ship and station keeps within the narrow limit of the 600-metre wave. Disconnecting the pin of the receiving-gear, and placing the jigger-switch on the first stop, he connected up the short-wave earth terminal. The sounds were of greater intensity but still fell short of the desired result. Deftly Mostyn manipulated the rack-and-pinion gear of the "Billi" until the signal became coherent.

Unconscious now of the girl's presence, Mostyn grasped a pencil and almost mechanically wrote the message that came through ethereal space. To her it conveyed nothing, being apparently a meaningless jumble of letters.

"SK—finished," announced Mostyn, then, again aware of Miss Vivian's presence, he continued. "Code message—they often send it in that form. I'll decode it straight away."

He tried with every code-book at his command, but without success. None of the recognized books afforded a clue. It might be just possible that Captain Blair would have a key in his possession.

"Sail on the starboard bow!" hailed the look-out man, just as the wireless operator dispatched a messenger to the Old Man.

At the hail Hilda left the wireless-room and went to the rail. Few ships had been sighted during the last two or three days, and her curiosity was aroused by the appearance of the stranger. Branscombe, who was standing near her, hastened to offer her a pair of binoculars, at the same time pointing to a small black object, surmounted by a blurr of smoke, on the horizon.

"What is the name of the ship?" asked the girl.

"Sorry, Miss Vivian," replied the Fourth Officer gravely, "but I'm not a thought reader. She'll probably make her number when she passes us."

The Donibristle was logging eleven and a half knots, and since the stranger was making eighteen or twenty it did not take long for the latter to become clearly visible to the naked eye. She was a light cruiser of about 4000 tons, with two funnels and two short masts. From the deck of the Donibristle it was seen that she carried a gun for'ard, and three on her starboard broadside, so it was safe to conclude that her principal armament consisted of eight 4- or 6-inch weapons. Right aft, and visible only when the superstructure no longer screened it, flew the White Ensign.

"What is she?" inquired Colonel Vivian.

"I can't tell yet," replied Captain Blair, who, having finished his conversation with the Chief, was making his way to the bridge with Mostyn's "chit" in his hand. "I don't even know her class. The navy's developed so many weird and hybrid types during the war, that it would puzzle Solomon to know t' other from which. Had them all at my finger-ends at one time. S'pose you don't recognize yonder cruiser, Mr. Burgoyne?"

"No, sir," replied the Third Officer, lowering his binoculars. "She hasn't even her name painted on her lifebuoys. Hello! Her bunting tossers are busy."

From the cruiser's bridge the International E.C. fluttered up to the signal yard-arm.

"That means 'What ship is that?'," explained Branscombe to Hilda. They had now crossed to where Colonel Vivian, Burgoyne, and several of the ship's officers off duty were standing.

"How interesting," muttered the girl. "What do we do now?"

"Make your number," replied Alwyn, loth to keep out of the conversation. "There it is: KSVT."

"That's not a number," objected Hilda.

"We call it a number," persisted the Third Officer. "Those four flags signify that we are the S.S. Donibristle, 6200 tons, registered at Newcastle-on-Tyne. Now they are making the next hoist—ATVH. That means Vancouver, our port of departure, and—by Jove, there's the ID."

Without waiting to give Hilda the interpretation of the two-flag signal, Burgoyne made a dash for the bridge, followed by Branscombe as a good second. Yet it was quite apparent to Colonel Vivian, his daughter, and Mr. Tarrant, that there was something of extreme gravity in that signal. Mrs. Vivian, being a little farther away, had not noticed the general exodus, while the remaining passenger—the drug drummer—showed no interest in the appearance of the cruiser.

Almost every officer and man on the deck of the Donibristle knew the significance of the signal. They had not served in the Outer Patrol during the Great War, when the examination of neutral merchantmen was an everyday occurrence, without learning to understand the peremptory command: "Heave-to instantly, or I will fire into you".

Such a mandate coming from a vessel flying the White Ensign was not to be treated with levity or contempt. Deeply puzzled, Captain Blair stepped to the engine-room telegraph and was about to ring for "Stop" when a startled voice—the First Officer's, although it was hardly recognizable—shouted:

"They're not bluejackets, sir; they're Chinks."

Just then the cruiser, which was bearing broad on the Donibristle's starboard beam, ported helm. Turning sixteen points, and moving half as fast again as the merchantman, she rounded the latter's stern and settled down on a parallel course at a distance of a cable's length on the Donibristle's port side.

"Tell the operator to send out a general SOS call," ordered Captain Blair hurriedly, "add 'attacked by pirate' and give our position."

He gave a quick glance in the direction of the cruiser. She had now drawn slightly ahead, so that she overlapped the Donibristle by about half her length. Meanwhile she had diminished speed until both vessels were moving through the water at approximately the same rate.

Just then a man scrambled on to the cruiser's bridge-rail and held a pair of hand signal-flags at the "preparatory". Then, without further preamble he semaphored: "If you use wireless I sink you".

The Old Man bent his head and spoke through the engine-room speaking-tube.

"Mr. Angus," he said in level even tones, "can you give me an extra two knots?"

Apparently the reply was favourable, for the skipper replaced the whistle with a gesture of satisfaction.

"Get the passengers down below, Mr. Burgoyne," he added; "there'll be sparks flying in half a shake. Heave-to, indeed. I'll show 'em how I heave-to. Pass the word for the hands to take cover."

Alwyn hurried off the bridge. He had barely reached the foot of the ladder when the pirate, aware that their commands with reference to the wireless had been disobeyed, opened fire with one of the beam 4-inch guns.

At that extremely short range it was almost an impossibility to miss such an easy target. With a terrific crash the wireless cabin simply disappeared, while fragments of the shell killed the Chief Officer on the spot, severely wounded one of the quartermasters, and gashed Captain Blair's forehead from his right eyebrow to his right temple.

The Old Man staggered, fell against the binnacle, and slid struggling to the deck. Branscombe rushed to his aid, but before he could reach him the skipper regained his feet. Half-blinded with blood, and dazed by the concussion, his one thought was the safety of his ship.

With a bound the Old Man sprang to the wheel, thrust the dumbfounded helmsman aside, and rapidly manipulated the steam steering-gear until the helm was hard-a-starboard. As he felt the ship answer he became as cool and steady as a rock. Deliberately he "met" and steadied her, until her bows pointed almost at right angles to the pirate's beam.

It was an audacious manoeuvre. The iron-nerved, tough old skipper was about to ram his opponent and send the cruiser, with all her rascally crew, to the bottom of the Pacific.