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.