"What would it be doing at Blacksnake Island? There's no doubt that it came from there."
"That's for us to find out. We'll let them go on to the mainland. Then we'll circle back and go up the other side of the island."
In a short time the other craft disappeared from view, entering a small cove some distance down the coast, and Frank turned their boat about and headed toward Blacksnake Island again. They approached it from the seaward side and drew in as close to the island as they dared. The rocky bluffs were lonely and forbidding, seeming to offer no available landing place.
"We'll go right around it. If Chet and Biff are there we should be able to see their boat or a fire or some sign of them," said Frank, half questioningly, to his brother.
"After seeing that other motorboat, I'm pretty sure we won't see any sign of them at all. I'm pretty well satisfied that those men kidnapped them and brought them here. And if they did, you may be sure they'll be well hidden."
"We'll circle the island anyway, and if we don't see anything we'll land and make a search of the place."
But making a circuit of the island took longer than the boys expected. Blacksnake Island was bigger than it had first appeared. It was almost a mile in length, and correspondingly wide—a great, swampy tract of forbidding marsh at one end, rising to higher ground and desolate rocks at the other. On the swampy side there were sinister little creeks, dead bushes half inundated, logs floating about in the black water. Frank and Joe caught glimpses of triangular black heads forging slowly through the water here and there.
"The blacksnakes!" Frank exclaimed.
Once the motorboat passed within a few yards of one of these black reptiles. Fascinated, the boys watched the ugly black head that projected above the surface, and they could see the long, sinuous body writhing beneath the water as the snake swam toward the fetid marsh.
"There must be hundreds of them on that island."