But the Professor shook his head. “The danger may exist in London equally,” he replied. “It is essential that someone I can trust should remain here. Otherwise, my boy, I should be more than pleased to take you with me. Now, listen very carefully to these instructions. Do not leave the house for long at a time, especially in the evening. Open all my correspondence, and deal with it to the best of your ability. Should there be among it any letter of a startling character, put a message in the personal column of The Times , ‘The asp has struck,’ and sign it ‘Cleopatra.’ Do you follow this so far?”

“Yes, sir,” replied Harold simply, but gazing at his employer in bewilderment. There was something theatrical about these extraordinary precautions utterly foreign to the Professor’s usual methods of procedure.