“If there was a three-letter word in the message,” he said, “we might get somewhere. That’s how the fellow in the story worked it. He found a lot of three-letter words, each of the same combination of letters, so he gathered that they would mean ‘the’ because the letter he thought meant ‘e’ was at the end of each. That gave him two more letters, ‘t’ and ‘h,’ to work on, and from there he found the cipher easy.”
“Mr. Sparewell was too smart for us,” said Joe. “He didn’t use ‘the’ in this message at all, from the looks of things.”
“I guess that scheme isn’t so good. Well, we have the notebook, and whoever lost it is sure to miss it and come back for it. I think it wouldn’t be a bad idea if we kept an eye on that place where the stores were hidden.”
“Catch him in the act!” said Biff.
“If the man is Sparewell, I guess Mr. Jefferson will be mighty glad to know where he is. The police have been searching for the man for fifteen years now. If it isn’t Sparewell, he’ll have a lot of explaining to do concerning this little book and how it came into his hands.”
“From now on, then, we keep a weather eye on those rocks,” Chet declared. “We ought to stand guard.”
“I don’t think that will be necessary,” said Frank. “It would only frighten him away. The best plan is to watch the place from here. We can easily see any one approaching the island and we can watch to see where he goes. If he heads for those rocks, we’ll know we have our man.”
“That means that some one has to stay on the island all the time.”
“I think it would be best. We can take turns at that, so it shouldn’t spoil our outing. Somehow, I don’t think we’ll have very long to wait. The moment that man finds his notebook is gone, he’ll hurry back for it.”
The other boys agreed that Frank’s plan was about the best that could be devised toward laying the mysterious thief by the heels. They were tingling with excitement because their outing on Cabin Island had plunged them into the depths of a first-rate mystery.