He paused to stare at a man who had entered the office. It was the man who had come there one time before — Terry Blake, of the secret-service.

“Perhaps I can help you,” said the new arrival.

“To find the source of the Double Z letters?” quizzed Cardona.

“Yes.”

“Where is it?”

“I can take you there.”

“When?”

“Now.”

“How many men will I need?”

“Bring two.”