The thing Joe saw took the form of a man. So far as the boys could see, he was rather neatly dressed in clothing which was wet with the wash of the river.
He was clinging to the side of the rowboat when first seen, but let go his hold and struck out for the shore. Evidently an expert in the water, he was halfway to the land before the occupants of either the Rambler or the rowboat recovered from their amazement and thought of stopping him.
Taking advantage of the darkness, the fellow had traveled for perhaps an hour, perhaps two, in the bottom of the rowboat. Then, when the boys had use for the boat, the only thing he could do was to take to the river.
They remembered that the rowboat had not been used since the robbers had been driven off with dynamite. The man might be a river pirate for all any member of the party knew.
The Rambler, being nearer to the swimmer than the other boat, at once turned her prow in his direction, but he reached shoal water before they overtook him, and disappeared in the thicket.
“Wouldn’t that frost you?” exclaimed Alex, bending over the edge of the boat and looking as if he expected to see more men where the swimmer had released his hold. “Say, but that man, whoever he is, can go some in the water!”
“I should say he could!” said Jule. “Where did he come from? Where did he go? If that act of his was a disappearing one, he certainly did it right!”
“I guess the Rambler obstructed our view,” explained Alex. “I’d like to know how long we’ve been carrying passengers, anyhow.”
The Rambler now returned from her fruitless quest of the stranger and anchored by the side of the rowboat.
“How long have you been leaking passengers?” Case demanded. “How many more have you got concealed in the boat?”