He came once more to the kitchen, and noticed that between it and the scullery was a closed door--the only door that remained in the house. Instinctively bracing himself, he turned the handle; the door opened, disclosing a dark hole and a downward flight of stone steps. He went down into the darkness, at the foot of the steps struck a match, and found himself in a low, spacious cellar, empty except for a strewing of coal dust. As the match flickered out he caught sight of something white in a corner. Striking another, he crossed the floor and picked up a jagged scrap of paper, slightly brown along one edge. At the same moment he observed a little heap of paper ashes.
Throwing down the match he trod upon it, and turned, intending to examine the paper in the daylight above. Pratt's voice shouting, and a sound of some one leaping down the staircase to the hall, caused him to spring up the steps two at a time.
"What's up?" he shouted back, unable to distinguish Pratt's words.
He reached the hall just in time to see Pratt dash through the doorway and sprint at headlong pace towards the river. Stuffing the paper into his pocket, Armstrong doubled after him. Pratt was already plunging into the thicket, and, when Armstrong came within sight of the channel, the other had flung off his cap and blazer, and was diving into the stream.
"THE OTHER WAS DIVING INTO THE STREAM."
"What mad trick----"
He cut short his exclamation, for his long strides had brought him to the pier, and he saw the cause of Pratt's desperate haste. The motor-boat, broadside to the stream, was drifting down the channel. Already it was some thirty yards beyond the spot where Pratt had taken the water, and Pratt was swimming after it with the ease of a water-rat.
Feeling that there was no reason why himself should get soaked too, Armstrong forged his way through the vegetation at the brink of the channel, but made slow progress compared with the swimmer. Pratt was rapidly overhauling the boat. Watching him, instead of his own steps, Armstrong tripped over a creeper, and fell headlong. By the time he had picked himself up, Pratt had disappeared. Armstrong's momentary anxiety was banished by the sight of the boat moving slowly in towards the shore of the island.
"Good man," he shouted. "You headed it off splendidly."