I was still examining the book when the door opened and the Professor entered. He was alone and for all I could see unarmed. My first instinct was to grapple with him but he met me with a smile which seemed at the same time to divine my impulse and to rebuke its folly. He sat down companionably in the vacant chair.
"A man in your position, my English friend," he said, "should only employ violence as the last expedient. Particularly," he sarcastically added, "as you are at present merely awaiting your release. Fritz will find a certain document at your hotel and you will give me a solemn promise to say nothing that might cause your poor dear grandmother to regret her hospitality. Then we shall just shake hands and part company."
"That's all very well," I grumbled. " But how can I be sure
