Willie stepped to his instrument and flashed the fleet call. Instantly the other boats responded. But it was needless to pass on the order. The other operators had likewise caught the _Morro Castle’s_ message to the _Surveyor_, and the patrol boats were on the alert. Now they quickened their speed. Back and forth they went across the tumbling waters. Now the fog lifted for a moment, but nothing was visible save the dull, distant glow of the _Morro Castle’s_ lights. Then the fog curtain fell again, blanketing everything. The wind blew in short, sharp blasts. The waves were beating on the shore and breaking with a never ceasing tumult of sound. Aboard the little fleet every ear was alert to catch the sound of motors, every eye was straining into the dark to single out some slightest gleam of light, some chance reflection that would betray the presence of the smugglers. Occasionally there was a lull in the wind. Once the roar of a motor was distinctly heard. It seemed to be close to the eastern shore. Then the sound was swallowed up in the tumult of the waves. The _Surveyor_ was stationed at the easternmost end of the patrol line. If the sound had been heard aright, the little boat must be directly in the path of the speeding power boats. The Chief stepped to Willie’s side. “Never mind your wireless now,” he said. “Come here and listen. We need your trained ear outside. We thought we heard the beating of a motor.” Willie threw down his head ’phone and stepped outside. At first he was deafened by the tumult of wind and water. His head ’phones had shut out much of the roar. In a few moments he became accustomed to the noise. He cupped his hand to his ear, held his breath and listened with all his might. But he could hear nothing save the tempest. Then the fog shut down again—a great, gray, blinding blanket of mist, that hid even the very waters alongside. “Listen!” cautioned Willie. He knew the carrying powers of fog. For a moment nothing was audible but the wind and wave. Then distinctly came the muffled roar of a motor. For a full five seconds it sounded. Then it was audible no longer. “It sounds as though it were close to this shore,” said Willie to his Chief. He had almost to shout to make himself heard. “Just what I thought,” said the Chief. “You can’t be sure, though,” said Willie. “Fog plays strange tricks with sound.” Wherever the rum runner was, it was evident that she was not far away. Certainly she was within half a mile. Probably she was nearer. Once more the fog lifted. Through the rift in the mist Willie made out some lights high in air. They were the lights of Quarantine. “We’ve drifted clear into the Narrows,” he called in his Chief’s ear. “We’re at the very narrowest part of the river.” “Good!” said the Chief. “Look!”