There was no sign of the motor boat. Evidently Stokes had returned to Death Island. It was not yet half past ten. But as Harry stood on the wharf, he heard the chugging of the motor — and the boat suddenly appeared around a point in the lake.
If Stokes was coming from the island, he had chosen a roundabout way. Harry thought quickly; then ducked back into the woods. He had a hunch that Stokes had docked the boat farther down the lake and had visited the village.
Waiting until the boat had pulled up at Harvey’s Wharf, Harry advanced along the path, whistling as he approached. He noticed the boat, and clambered aboard, without even greeting the man who was at the helm.
That seemed to suit Stokes. He gave no sign of welcome. He piloted the boat directly back to Death Island. Harry handed him the flashlight, with the single word: “Thanks.”
DEATH ISLAND was black and silent as the boat approached. No twinkling lights to-night; no phantom shapes. There was no sign that anything out of the ordinary existed in that tract of land that loomed from the center of Lake Marrinack.
Stokes went in to Professor Whitburn’s study, when they had reached the house. Harry took it that he was reporting their return.
After a half hour of reading, Harry decided to go to bed. He went upstairs, and as he passed, he noted that the door that led to the tower was ajar.
Harry’s room was under a corner of the tower. He had been conscious of that fact the night before. It had troubled him; yet it had indicated nothing. But to-night, he seemed to detect a faint tapping on the ceiling of his room. It continued intermittently; then stopped.
The sound was peculiar, yet methodical. The taps came in rhythmic beats. They could not be made by any one working, for they changed their rhythm too often.
Finally the sound ceased. Five minutes passed. It began again; then stopped. Another interval, of perhaps five minutes. Again a short series of taps.