"No stray plane landed or even flew over here last night so far as I could learn. Most of the boats on the bay were either known or lent themselves to ready identification. There were four that I couldn't exactly place, but I think we can safely discard all but one. Some fishermen were pulling nets on the bay about half a mile outside the mouth of the Bush River last night. About eleven, a boat running without lights passed them. They said that they could not hear an engine running, but just a dull hum and the gurgle of a propeller. They hailed it, but got no answer. It faded away into the darkness and they think it was headed toward the mouth of the Bush River. They had their nets up and reset in another hour but the boat didn't reappear." "Hmm. High tide was at ten minutes after midnight. There was plenty of water in the river at that hour. It sounds promising." "I thought of telephoning Washington and getting a Coast Guard cutter put on patrol in the bay but I didn't like to do it without your sanction." "It might have been a good idea, but on the whole it's probably better that you didn't. Carnes, we'll go down to the water front and see whether anything shows up to-night. High tide will be about eleven-thirty. It's about half-past nine now. We'd better get going." * * * * * On the second drive to Michaelville, the fog patches were quite noticeably denser than they had been earlier in the evening. Three times the car had to pass through bands of fog which covered the road. As they passed the second one Carnes suddenly began to cough. "What's the matter, old man?" cried Dr. Bird, a note of anxiety in his voice. For a few moments Carnes could not answer for coughing. He seized the mask to tear it from his head but Dr. Bird restrained him. In a few minutes his voice became intelligible. "It seemed like that fog bit right into my lungs, Doctor," he gasped. "I felt as if I were choking. It's better now." "Are you sure your mask isn't leaking, Carnes? It'll be all up with you if it does. Test it." The detective closed the intake valve of the mask and expelling all of the air from his lungs, took a deep breath. The air whistled noisily in through the outlet valve. "The devil!" cried the doctor. "Take that mask off and let me look at it." A few moments were enough to make the needed repairs and they drove on. Carnes still coughed from time to time. At Michaelville, they started the scooter and ran down the track to the river. They secreted the scooter under the parapet on the water pent-house and walked to the river's edge.