"With the serving of the soup he forgot her and went on with his dinner. That over he paid the waiter, strolled out to the street and called a cab. When it drove up the veiled woman stood beside him.
"'I think this cab is mine, sir,' she said in excellent English.
"The Engineer raised his hat, offered his hand to the woman and assisted her into her seat. When he withdrew his fingers they held a small card edged with black. The woman and the cab disappeared. He turned the card to the light of the street lamp. On it was written in pencil, 'Meet me at Café Ivanoff at ten to-night. You are in danger.'
"The man read the card and strained his eyes after the cab; then he called another, drove down to the station, picked up his trunk, and started for the Hotel Metropole.
"On the way to the hotel he kept thinking of the woman and the card. It had not been the first time that his fresh cheeks and clean-cut features had attracted the attention of some woman dining alone—especially in a city like Vienna; any continental city, in fact. Some of these adventures he had followed up with varying success; some he had forgotten. This one interested him. The proffered acquaintance had been cleverly managed. The warning at the end was, he knew, one of the many ruses to pique his curiosity; but that did not put the woman out of his mind.
"When his baggage had been deposited in his rooms, a small salon, bedroom, and dressing-room, all opening on the corridor—he needed the salon in which to lay out his plans and maps—he gave his hat an extra brush, strolled downstairs, and stepped to the porter's desk.
"'Porter.'
"'Yes, sir.'
"'Where is the Café Ivanoff?'
"'Near the Opera, sir.'