“Of course.” She regarded him gravely with her big blue eyes. “You knew where it was all the time, and to think that I did not guess? Poor Marie Lou!”

“Look here, fooling apart, I want to talk to you.” Rex spoke earnestly now, and for a few minutes they spoke together in low tones.

“O.K.” He got to his feet again. “I’ll be back half an hour after sundown, or an hour at the latest. Be a good kid and keep the Duke amused while I’m gone. He’s that jumpy he can’t keep still.” With a wave of his hand Rex disappeared into the ruins at the far end of the passage.

Marie Lou went back into the foundry. Rex was right about De Richleau. In the hour of action the Duke could be relied on to be utterly calm — his self-possession under fire had filled Simon with amazement Even Rex, whose nerves had all the perfection of bodily fitness and youth, could not exercise the same calm judgment in a crisis. But these days of forced inactivity had played havoc with his accustomed serenity. He paced softly up and down — up and down — the centre of the room, like some powerful caged cat.

From morning to night he was revolving in his mind the problem as to how they could leave this dangerous forbidden territory with speed and secrecy — his brain was stale with it, and the more he thought the less likely it seemed that fresh ideas would come. He knew that, himself, yet he could think of nothing else, and that made him still more nervy and irritable.

Marie Lou drew him outside into the slanting sunlight. “Come and talk to me,” she begged. “You think too much — it is not good.”

He smiled, with something of his old charm. “What would you have me talk about Princess?”

“What you will. Tell me about Paris.”

“Ah, Paris....” He leant against the wall. “Paris is a hundred cities. There is the Paris of Henry of Navarre, the Paris of the Grand Monarch, the Paris of the Revolution.”

“No, no, tell me of the Paris of today.”