"It's I--Mr. Jenks," was the surprising answer.

"Mr. Jenks?" repeated Tom.

"Yes--Barcoe Jenks, of Earthquake Island."

"You here? What do you want?"

"Can you come down?"

"What for?"

"Tom Swift, I've something very important to tell you," was the
answer in a low voice, yet which carried to Tom's ears perfectly.
"Do you want to make a fortune for yourself--and for me?"

"How?" Tom was beginning to think more and more that Mr. Jenks
was crazy.

"How? By helping me to discover the secret of Phantom Mountain,
where the diamonds are made! Will you?"

"Wait a minute--I'll come down," answered Tom, and he began to
grope for his clothes in the dim light of the little electric
lamp.

What was the secret of Phantom Mountain? What did Mr. Jenks
really want? Could he make diamonds? Tom asked himself these
questions as he hastily dressed to go down to his midnight
visitor.