Only the hand now showed above the surface.  Finally that, too, disappeared beneath the waves.

Despairingly she turned to see if there was anything on the dock with which she might help Locke—­and she saw the Automaton himself advancing from the shore toward her.  She turned.  The emissaries on the other end of the dock cut off any chance in that direction.

Without a moment’s hesitation Eva poised herself a moment on the edge of the dock and leaped far out into the blackness of the river.

CHAPTER XIII

The box that held Locke a prisoner was now undoubtedly resting on the slimy bottom.  Eva had totally disappeared.  The Automaton, convinced that at last he had rid himself of his victims, waved away the emissaries and departed.

Except for the tiny lights of ships on the river and the staccato exhaust of a tugboat, the river flowed with nothing to remind one of the two tragedies of only a few seconds ago.

As far as the eye could see, the surface of the water was unbroken.  Then, suddenly, the scene changed.  For from out the water, as though hurled up by a catapult, shot a man’s body.

It was Locke.

By what miracle had he escaped from the watery grave?

From the time he was a small boy the study of locks and bolts, of knots and strait-jackets, of anything that could restrain or bind a man, had held a marvelous fascination for him, until now he was recognized as one of the world’s greatest experts on these subjects.  The great lock concerns often sent for him to test new inventions, and invariably he could point to any flaw in the constructions of them that existed.  As he came to manhood his knowledge had grown apace until to many he seemed a veritable sorcerer.

It was by a trick known only to himself that he had been able to extricate himself from his desperate plight at the river’s bottom.  True, his flesh was lacerated.  True, he was on the verge of total collapse.  But he lived.

He made his way slowly toward the dock and was resting against one of the piles when he heard a faint cry.  He strained his ears to locate the direction whence it came.  Once again that feeble call floated across the water, and in it there sounded something vaguely familiar.

He was more rested now and he swam farther under the dock.  Again came the cry.  With a thrill now he recognized the voice.

“Eva!” he called, again and again.

“Here I am,” came back the echo.

With a powerful stroke he breasted the current and in a moment he was supporting her half-fainting body.  Precarious though their position was, Locke felt the thrill of her words.  The effect was to spur him on to fresh efforts.

Eva had become stronger now.  For a few moments he swam, in order, if possible, to find some means by which they might escape from the water and reach the dock.