He offered Gerstein a liberal share of the treasure if he would divulge its whereabouts and tell what had become of the Raven and her crew.
Gerstein declined to say a word. He simply regarded the captain in a mocking, insolent way. It was evident that the fellow appreciated the full value of his knowledge concerning the treasure.
"He's counting on getting away from us somehow, before the cruise is over," reported Captain Broadbeam to his friends, "or he is taking chances on our running into a nest of his friends when we reach the Windjammers' Island."
The Swallow had a delightful run to Mercury Island. Before they reached it Gerstein was placed in the hold, and there closely guarded by two mariners until they had provisioned up and were once more on their way.
Dave had little to do except to wait the end of their cruise, yet he put in some busy hours. For three days he kept Stoodles at his side at the table in the captain's cabin, questioning him on every detail about the lay and outlines of the island they were sailing to. Then he made a chart of the island, and as near as possible from memory marked in the other island where they had recovered possession of the Swallow after it had been stranded during a cyclone.
The weather changed suddenly a day or two out from Mercury Island. They rode into a fierce northeaster, and it rained nearly all the time, with leaden skies and a choppy sea.
Dave was a good deal below. One afternoon, returning from a brief visit to Bob Vilett, as he was making for the cabin passageway, a chink of light attracted his attention.
It emanated from a crack in the paneling of the cabin occupied by Gerstein. Dave drew nearer to the chink, and could look quite clearly into the compartment that housed the person in whom he was naturally very much interested at all times.
"H'm!" said Dave, with a bright flicker in his eye. "He's making a chart, too, is he?"
The daylight was so dim that Gerstein had a lighted candle on the table at which he sat. Spread out before him was a sheet of heavy manila paper. It bore black outlines as if an irregular body of land, and had crosses and dots all over it.