“I could tell that exhaust of hers anywhere,” explained the engineer. “It’s the worst on the river.” For some time they listened to the coughing of the _Piedmont_. The _Vixen_ was barely creeping along, for it was impossible to make any speed; the danger of a collision was too great. “She seems to be cruising up and down,” said Kenyon. “Yes; her skipper knows that this is about the best place to meet any vessel making for the Sound. They come this way to avoid the currents around Hell Gate.” Backward and forward cruised the _Vixen_ passing and repassing the _Piedmont_ in the darkness. Once those on board the latter seemed to become suspicious, and she crept forward, her port and starboard lights shining through the fog. “Hello!” cried a voice. “Who is that?” “Don’t come any nearer,” replied the skipper of the _Vixen_. “I know how that old box of yours steers, Morgan.” “Oh, is that you, Phylen? All right.” And then the _Piedmont_ crept away again, resuming her cruising up and down. At this point Dallas re-appeared upon deck. “I thought I heard someone calling,” she said. “You did,” answered Kenyon. “We’ve come up with the other boat that the captain was telling us of.” She gave a little gasp and looked off in the direction of the now distant boat. “Do you know,” she whispered in a frightened sort of way, “that sound out there reminds me of the cough of Hong Yo.” She had placed her hand upon his arm, and he could feel the shudder that ran through her. “Oh, how I fear that man.” “You have excellent cause. The man from Butte was close to the truth when he called him a dying devil.” She gave him a quick, surprised glance but said nothing. “The murder of that man was one of the worst exhibitions of deadly ferocity that I ever saw--and my career in South America was not without its experiences.” “It was dreadful,” said the girl, shudderingly, and she covered her face with her hands. Now and then a steam vessel would pass them in the darkness, and the skipper of the _Vixen_ would hail its deck and draw alongside. But they were mostly tugs and “truck” boats; as yet no yacht had split the murk. “Do you feel quite sure that she has not yet gone by?” asked Webster at length. “I’m positive of it,” replied Kenyon. “She had not the time. But she should be due at almost any minute now.” “Hark, there!” cried the skipper; “do you hear that whistle?” There came a low, mournful wailing from down river. “It’s one of those toy sirens that some yachtsmen fit their crafts with,” the skipper informed them. “Like as not this is the vessel you want.” “Yes; and there goes the _Piedmont_ for her,” said Webster. The coughing exhaust of the unseen power-boat gurgled and volleyed from ahead; and they could see her port light streaming dimly through the fog.