"Naturally," Korvin said in a friendly tone.
The expert frowned horribly, showing all of his teeth. Korvin did his best not to react. "Your plan is a failure," the expert said, "and you call this a good thing. You can mean only that your plan is different from the one we are occupied with."
"True," Korvin said.
There was a short silence. The expert beamed. He examined the indicators of the lie-detector with great care. "What is your plan?" he said at last, in a conspiratorial whisper.
"To answer your questions, truthfully and logically," Korvin said.
The silence this time was even longer.
"The machine says that you tell the truth," the experts said at last, in a awed tone. "Thus, you must be a traitor to your native planet. You must want us to conquer your planet, and have come here secretly to aid us."
Korvin was very glad that wasn't a question. It was, after all, the only logical deduction.
But it happened to be wrong.