At 11.15 one morning a startling incident occurred that, rightly or wrongly, was attributed in some manner to Captain Restronguet.

It was on Southsea beach, almost midway between the pier and the castle.

The beach and parade were thronged with people, mostly visitors who had taken advantage of the Fleet's presence to enjoy the view of the ships.

The sea was perfectly smooth, being unruffled by the light off-sh.o.r.e breeze; the tide was, however, running very strongly, for it was about the fourth hour of the ebb.

Suddenly a succession of shrieks from a group of children paddling in the water attracted the attention of persons in the vicinity, and to the astonishment of every one the head and shoulders of a man encased in a dull green metal helmet emerged from the waves.

For a few moments the man hesitated, then staggered out of the water.

At the edge of the beach he sat down and began to remove his head-dress, that the onlookers noticed was unprovided with air-tube or life-line.

He was apparently quite independent of an outside air-supply.

Surprise had hitherto kept the spectators at a respectful distance, although their numbers were momentarily increased by others, until a deep semicircle of gaping onlookers hedged the diver in on the landward side. But as soon as he began to take off his helmet the crowd swayed nearer and nearer.

The removal of the metal head-dress revealed the features of a man of about thirty years of age, clean-shaven and with closely-cropped dark-brown hair that had a tendency to curl. Without speaking a word the unknown drew a knife from his belt and began to hack rapidly at some contrivance at the back of his helmet. As soon as he had severed the part he was attacking he stood up and hurled it far into the sea. This done he calmly began to strip off the stiff fabric that composed his diving suit.

By this time the coastguard on duty at the look-out hut had noticed the crowd congregate, and through his gla.s.s saw that something unusual was happening and that a diver had come ash.o.r.e. Since there were no Government diving boats anywhere in sight he naturally thought that it was a case for investigation, and the detachment of coastguards was promptly turned out.

"Here, sir, what's the meaning of this?" demanded the chief officer, forcing his way through the crowd. "Who are you, and how did you manage to get ash.o.r.e here?"

"That I can easily explain," replied the unknown. "I am an inventor, and this diving-dress represents the result of seven years' work. I walked into the sea at Gosport a couple of hours ago, but, getting caught in the strong current running out of Portsmouth Harbour, I was swept a great distance until I managed to regain my feet. By walking in a direction due north as shown by my watertight compa.s.s I came ash.o.r.e here. Needless to say I do not look for publicity, and all I wish is to pack up my discarded gear and go."

The chief officer looked at the stranger with mingled astonishment, admiration, and doubt. Never before had he known of a diver covering a distance of more than two miles, and that without the a.s.sistance of a boat containing the necessary apparatus for supplying the submerged man with air.

"Hanged if I know what to make of it, Smithers!" he said in an aside to his leading petty officer. "Perhaps he's a spy, or one of that blooming Captain Restronguet's crowd. This beats all creation!"

"Can't we detain him on suspicion?" asked Smithers. "I'll swear he's up to no good."

"I've half a mind to," replied the chief officer dubiously. "But, you see, they'll come down on me like a hundred of bricks if I exceed my duty."

"Invite him to the station, friendly-like," suggested the petty officer, "then, while he's there, you can telephone for instructions."

"I'll try it, by smoke!" e.j.a.c.u.l.a.t.ed the chief officer, and approaching the unknown he asked if he would like to dry his clothes at the coast-guard station, since his ordinary garments, owing to the exertion in a confined s.p.a.ce, were dripping with moisture.

"No, thank you," replied the submarine pedestrian. "All I want is to get a taxi, and make myself scarce. The attentions of so large a crowd are really embarra.s.sing, and I am a man of a very retiring disposition.

Had I expected this reception I should have vastly preferred to have landed in a more secluded spot."

With that he ignored his questioners and began to roll his diving suit into as small a compa.s.s as possible.

The coastguards were on the horns of a dilemma. They feared to make an unlawful arrest, while they might be severely brought to book for allowing the stranger to slip through their fingers, but there was nothing in the King's Regulations to prevent a man landing on a public beach, whether from a boat, hydro-aeroplane, or otherwise.

Just at that instant a policeman strolled leisurely up, and scenting a charge, produced his notebook and pencil.

"Hi! What's this you're up to?" he demanded, but the unknown totally ignored him.

"Can't he speak English?" asked the policeman of the coastguard officer.

"Rather," a.s.serted the other emphatically; then in a lower tone he added, "Look here, we want to detain the man, but we cannot name a charge."

"I'll see about that," retorted the policeman. "Now, sir, your name and address, please."

"Allow me to inform you, constable, that my name is not 'Hi.' Since you addressed me as such you must not be surprised that your question was ignored."

A t.i.tter went up from the crowd, which had the effect of rousing the ire of the representative of the Law.

"Now, sir, your name and address, please."

"What for, constable?"

"For bathing off a public beach in prohibited hours."

"Don't talk rot!" exclaimed the unknown indignantly.

"Very good; since you refuse I have no option--I arrest you. Any statement you make may be used as evidence against you. Come along with me."

Attended by the surging crowd the policeman escorted his charge to the road, where a cab was hailed. The chief officer of coastguards was requested to accompany the prisoner as a witness, and the three entered the vehicle and were driven to the police-station.

Here, in order to gain time, the prisoner was formally charged with unlawful bathing, and as the Court was still sitting at the Town Hall he was ordered to be taken there at once. The chief officer meanwhile communicated with the naval authorities by telephone, expressing his opinion that the diver was a member of the mysterious Captain Restronguet's submarine.

But the prisoner never arrived at the Town Hall. When the cab stopped outside the court a policeman was found insensible on the seat. The floor had been violently ripped up, and unknown to the driver and the constable on the box the suspect had got clean away. By some inexplicable agency the unknown had deprived his captor of his senses, and the mystery of Captain Restronguet had entered into another phase.

CHAPTER IV.

THE SIGNAL FROM THE DEPTHS.

"Naval appointments: The following appointment was made at the Admiralty this afternoon: Sub-Lieutenant Arnold Hythe to the 'Investigator' for special duties (undated)."

This item, in the Stop-Press columns of an evening paper, was shown to Sub-Lieutenant Hythe by one of his brother officers.

"You are a lucky dog!" exclaimed the latter. "My Lords evidently recognize your capabilities as a diver. Well, good luck, old man. I hope you'll play the chief part in running down this plaguey fellow.

Hang it all, I cannot see that he's doing any harm, except that all leave is stopped until something is done to stop his little antics."

"Yes, that is hard lines," a.s.sented the sub. "But I'll do my level best, no doubt."

H.M. surveying vessel "Investigator" was lying in dock at Portsmouth, and was under orders to proceed to sea at the first possible opportunity, her errand being to endeavour to locate and capture the submarine that, it was generally agreed, was still in the vicinity of Spithead.

To cope with the situation a special Bill had been hurriedly introduced into Parliament making it an offence against the Naval Secrets Act for any person to manoeuvre a private submarine within five miles of specified naval ports. The Bill received the Royal a.s.sent and became law within thirty-six hours after the escape of the suspect arrest on Southsea beach, an individual who was generally accepted as being the man of mystery, Captain Restronguet.

The fellow's diving gear, or at any rate the major portion of it, remained in the hands of the authorities. After being subjected to a lengthy research at the hands of the Diving School at Whale Island the following report was issued confidentially: "The helmet is of a metal hitherto unknown, possessing all the advantages of aluminium, without the known disadvantages. It is a departure from the usual form, having a ridge-shaped projection in front, possibly to lessen the resistance to the water when moving on the bottom of the sea. The helmet is also valveless, the air, chemically prepared, is by some means kept at a fairly high pressure, sufficient to distend the suit in order to do away with any discomfort to the wearer by reason of the weight of water. The suit is made, not of rubber as was at first supposed, but of an unknown quality of flexible metal. When distended it also presents an edge in front, in order to minimize lateral resistance. How the air is purified is still a secret, the apparatus for so doing having been detached and thrown into the sea by the unknown. A diligent search had failed to produce this important item. Undoubtedly the suit, when complete, is far in advance of any now used in the Service."

A careful watch was maintained along the sh.o.r.e, the coastguards stationed in the district being temporarily augmented by men drafted from more remote places. Yet no trace of the mysterious submarine on the surface was to be seen. How, when and where the craft replenished her fuel necessary for locomotion purposes and her provisions and fresh water completely baffled the naval experts; for a fortnight had elapsed since she announced her appearance at Spithead, and save for the temporary visit to Cherbourg all evidence pointed to the fact that she was still within the limits of the Port of Portsmouth.

Arnold Hythe duly joined the "Investigator" as officer in charge of the diving parties. Twelve first-cla.s.s seamen-divers were drafted into the ship, while special gear for "creeping" was placed on board. Submarine apparatus for recording by sound the presence of submerged craft under way was also installed, so that it was impossible for any vessel making the faintest noise to approach within two miles of the "Investigator."

Even the wavelets lapping the bows of a pa.s.sing fishing-smack would be reproduced with unerring fidelity. Just before high water the "Investigator" was undocked; steam was soon raised, for the surveying vessel, being of an old type, was driven by reciprocating engines and oil-fed boilers. Almost at the moment of casting off the hawsers and springs came news that caused the greatest disappointment amongst officers and crew.