“They have quit signaling,” reported Tom.
“What do you make of that other ship’s continued interest in us, captain?” asked the professor.
“I’m blessed if I know,” he replied. “It’s too deep for me. They have been following us ever since we left the bay, and I’m blessed if I don’t think they are after us. But I cannot imagine for what purpose.”
“I suspect,” said the professor, “that they have some knowledge of the fact that we are after a treasure.”
“Oh,” said the captain, “but they can’t expect to keep us under observation for a long trip like this. It would be ridiculous.”
“What they want most likely is the chart. Only with its aid can anyone locate the island or the treasure.”
The captain sat for a few moments in thought. “There must have been somebody on board getting the signals. Now who could it be?”
“One of the crew,” suggested Tom.
“Quite likely,” agreed the captain, “unless—”
“What?” said the professor.