"What reason have you for thinking so?"
"I decline to state."
"Who do you think wrote it?"
"How should I know?"
"As you know so much, I don't mind telling you that you are right. The letter was a hoax."
Sam laughed heartily.
"I thought so," he said.
"And I know who wrote it."
Sam didn't laugh now.
"Who?" he asked uncomfortably.