Slowly they drew away from the dread spot, and soon came to a more populous locality where the lights of honest shops and peaceful homes gave them a sense of greater security and brought a feeling of unreality to the horrors through which they had passed.

A taxi-driver hailed them, and in a short time they were rolling along the Cliff Drive and had arrived at Brent Rock.

It was the following day that the old butler handed Locke a letter addressed to International Patents, Incorporated, from the Diving and Salvage Company. Locke was about to read it, when Eva entered and they read it together.

"We are reliably informed," read the letter, "that the Under Seas Corporation is trying to obtain possession of the self-liberating diving-suit which you control in our interest. This must be prevented."

Locke was immediately interested. At once it occurred to him that here was a patent which the company had suppressed which might prove of incalculable value.

"This suit might be very valuable to the government," he exclaimed to Eva. "I am going to try it myself."

"Please don't," pleaded Eva. "It isn't worth it. It's not worth the risk."

Locke, however, realized that here was something of extreme importance, and as he visualized to Eva the helplessness of a deep-sea diver, his air-line cut, struggling in vain to release himself and rise to the surface, he began to win her over.

At the moment when Quentin and Eva were in the library, Zita was taking advantage and was ransacking Locke's laboratory, not with any definite purpose in mind, but searching in every nook for some clue which might tell her what he was about.

The speed with which she worked was extraordinary. Yet, before she moved an instrument, a retort, a book, its position was minutely studied, so that she could restore it to its former place without any one suspecting that it had ever been moved.

It was while she was thus occupied that her eye fell upon an instrument which aroused in her an excited interest. It was very like the headpiece used by operators of telephones, and she hastened to adjust it. In a moment it was as though she were in the library. She could hear Locke's earnest laugh and in it Zita could detect an undercurrent of tenderness.

Her lips compressed and her eyes hardened as she listened. Locke was speaking about a letter and it seemed to be something important. Zita was all ears.

But Locke's next words which she heard were his decision to test the diving-suit, and as she listened she became tense, for this information she knew was important. The continued note of tenderness in Locke's voice more infuriated Zita. She removed the headpiece of the dictagraph, slammed it back into the desk drawer from which she had taken it, and hurried out.

In the library, Locke, having persuaded Eva, left her and went down into the Graveyard of Genius, where he touched the secret spring and the massive door flew open. He entered the gloomy place and went at once to the shelf upon which lay the self-liberating diving-suit. He took the suit down and examined its every detail minutely. As he did so he became more and more enthusiastic and he could find no fault with any of its features.

"It's entirely practical," he exclaimed to himself. "I'm going to try it to-day."

He closed the great door and remounted the stairs, carrying the suit with him. But had he noticed the fiery eyes that had watched him through the secret rock door of the cavern he would not have been so eager to try the test he had in mind.

By this time Eva had called her car, and together Locke and Eva drove to the near-by cove, where there was a little launch which he planned to use.

Out into the river they sailed, Eva at the wheel, while Locke busied himself over the sputtering engine. Soon they arrived at a spot which was suitable for the test of the suit.

Locke had brought along the full equipment, and, while Eva took charge of the air-pump, Locke donned the diving-suit. Soon all was ready and Locke descended over the side, after carefully instructing Eva in each detail. Eva started pumping, while with her other hand she carefully paid out the air-line and signal-cord.

But in their close attention to the task in hand, neither had noticed a low, knifelike launch that had followed them and that was now hovering a short distance off.

Locke was now walking over the shell-strewn bottom, examining curious objects here and there. The tide was setting in strongly and at times it was with difficulty that he kept his feet.

He had become satisfied that this particular suit filled all the requirements of a first-class diving-suit, and he was about to try its special, self-liberating feature, when his attention was arrested by a vague mass which seemingly moved against the current.

This was so extraordinary that his first thought was of a shark. He stopped in his tracks and became motionless, for it is a well-known fact that these sea tigers rarely see an object unless it is in motion.

Still, the vague form slowly took on more distinctness as in its course it gradually drew nearer to him. It was then that Locke was almost overcome with surprise. For there, groping his way toward him, was a diver, like himself.

What was this strange being doing there on the bottom of the sea? Whence had he come? Locke could not guess. For, like Eva, he had not noticed the other launch. It seemed impossible to him. Still, to him, apart from curiosity at the appearance of the other diver, the incident had no other interest. What had he to fear from any man at the bottom of a peaceful harbor? Locke moved nearer.

The stranger allowed him to approach, stopped, even, as though he were himself amazed at Locke's appearance, and Locke made gestures to reassure the man of his good intentions.

Locke was quite close now, and through the glass gate in the other's helmet he could see his eyes. But in those eyes he could see no responding friendliness. There was a murderous hate instead. He tried to step back and place himself in a position for defense, but he was too late. For, with a movement amazingly rapid for one under water, the stranger leaped upon him, at the same time drawing a long knife. There, under the sea, commenced a battle royal.

Locke was unarmed and so from the start was at a disadvantage. The stranger seemed not so anxious to stab him as to come to close quarters, and before Locke could prevent him he had done so. With his left hand he grabbed Locke's lines, while with the other, in which was the keen knife, he slashed murderously.

Locke tried to break his grip. But the other was not to be denied. With one stroke he cut through both lines, pushing Locke backward and himself springing free at the same time.

Immediately Locke's helmet filled with sea water, while the pressure became enormous. Locke tried to hold his breath, while his hand searched for the liberating knob. He gave it one twist. It worked perfectly.

Locke's suit, including the helmet, simply opened and fell from him.

Propelled as much by the pressure that the water exerted as by his own powerful strokes, Locke shot to the surface.

The day was perfect and the bay was calm. For a few seconds Locke floated, drawing the air into his starving lungs. Then he raised himself and gazed about him. At first glance everything seemed the same except for the fact that, whereas before his own boat had been alone, there were now two. Then Locke heard an agonizing call for help--from Eva.

After he had gone over the side of their launch Eva was naturally very intent upon keeping him plentifully supplied with air. He had been down some time before, glancing about, she had spied the other launch. But at the time she had thought little of it. For her, all thought of danger was centered on the man who was now risking his life many fathoms beneath her from pure motives of patriotism.

It was only, some minutes later, when she heard the grating of another boat against the side of her own that she realized that she herself stood in danger. But even at that moment her thoughts were of Quentin, who now for the first time was wholly dependent on her efforts alone.

She looked up fearfully, and what she saw fairly congealed the blood in her veins. Directing a murderous emissary to board Eva's launch, in the cockpit of the other boat stood the Automaton!

Not for an instant did Eva cease her efforts at the pump. But she shrieked with terror again and again. Now, to add to that terror, the pressure on the air-pump suddenly ceased. From the depths myriads of bubbles of air arose.

Knife in hand, the emissary leaped aboard and came toward her.

Automatically, frantically, she still turned the useless pump, while with her free arm she tried to ward off the poised knife.

Again her shriek for help echoed across the water--and this time her call was answered.

Had she gone mad? The voice that answered her was the voice of the man she loved. Her brain reeled and she fell at the feet of the murderous thug.

Other cries, then shouts were now heard, for some fisher folk were putting out off shore to discover what all the tumult was about.

The Automaton made a hasty gesture to the emissary, who sprang back from his victim and leaped to his own launch, where, with his assistance, there was barely time to haul aboard the chief thug, who had been sent below to attack Locke. The launch cast off and with ever-increasing speed headed down the river.

Locke was the first to arrive and climb over the side of the boat.

Dripping though he was, he took Eva in his arms and bathed her face, while by this time other craft arrived and friendly hands did all they could to care for them both.

It was some minutes before Eva was restored and all headed again to the shore, eager to help Locke.

As he assisted Eva to land, and they waited for a carriage, Locke hastily offered a boatman a liberal reward for the discovery of the precious diving-suit, for it had been his intention to present the patent to the government.

Meanwhile some strange things had happened. Paul and his father had quarreled over money, over De Luxe Dora, over Paul's manner of life and his ill luck in winning Eva's affections.

At the same time Dora had become more insistent in her demands for money to meet her extravagances, and Paul conceived an idea of selling one of the patents to a rival company. Strange to say, it had been the self-liberating diving-suit and the rival company was the Under Seas Company.

All this took place some time after the disappearance of the Automaton and his precious crew.

Some hours later that evening a telephone message came for Locke from the boatman that the diving-suit had been recovered and was being held by him.

Locke replied that he would be down in an hour. But during that hour other strange things occurred. For no sooner had the boatman hung up his receiver than a pleasant voice hailed him and he left his house to investigate. It was Paul Balcom.

It was in a clever, insinuating, affable manner that Paul approached the real object of his visit. His appeal was cleverly worded, cleverly presented. The sole object was to awaken the poor boatman's cupidity.