It was three o'clock in the morning. Along a deserted pavement of Riverside Drive strode briskly a young man whose square-set shoulders and erect poise suggested a military training. His coat, thrown carelessly open to the cold night wind, displayed an expanse of white indicative of evening dress. As he walked his heels clicked sharply on the concrete with the forceful firm tread of the type which does things quickly and decisively. The intense stillness of the early morning hours carried the sound in little staccato beats that could be heard blocks away. A few yards behind him, moving furtively and noiselessly, almost as if he had been shod with rubber, crept another figure, that of a stocky, broad-shouldered man, who despite his bulk and weight moved silently and swiftly through the night, a soft brown hat drawn low over his eyes as if he desired to avoid recognition.

All at once the man ahead paused suddenly and stood looking out over the river. Between the Drive and the distance-dimmed lights of the Jersey shore there rose like great silhouettes the grim figures of several huge steel-clad battleships, their fighting-tops lost in the shadows of the opposite hills. Beside them, obscure, with no lights visible, lay the great transports that in a few hours, or in a few days--who knew--they would be convoying with their precious cargo of fighting men across the war-perilled Atlantic.

It was on the forward deck of one of these great battleships that the eyes of the man ahead were riveted. His shadower, evidently much concerned in his actions, crept slowly and stealthily forward, approaching nearer and still nearer without being observed.

A dim light became visible on the warship's deck and then vanished.

Still the man stood there watching, a puzzled, anxious look coming into his face. Quickly the light reappeared--two flashes, a pause, two flashes, a pause, and then a single flash. It was such a light as might have been made by a pocket torch, a feeble ray barely strong enough to carry to the adjacent shore, a light that if it had been flashed from some sheltered nook by the boat davits might not even have attracted the attention of the officer on the bridge nor of the ship's watchmen.

Manifestly it was a signal intended for the eyes of some one on shore.

A muttered imprecation escaped the lips of the watcher on the Drive. He stood there, straining his eyes toward the ship as if expecting a following signal, then he turned and gazed aloft at the windows of the apartment houses lining the driveway to see if some answering signal flashed back.