Many times had I flown over Cornwall; never had I set foot in the Duchy until now. Plymouth had always been my furthest west.

The sea was blue as the Mediterranean, the sky a huge hollow turquoise, the air all Arabia. Away in the bay St. Michael's Mount, crowned with towers, gleamed like a vision of the New Jerusalem in some old monkish missal—and the heart within me was so hard, stern, and full of deadly purpose that no summer seas nor balmy western winds could touch the rigour of my mood.

For we were on the battlefield now. There was no more vagueness nor speculation. I, in the place I occupied, owed a debt to society, and to myself a personal and bitter revenge. And those debts should be paid.

Danjuro knocked and entered the bedroom. Yesterday afternoon, within half an hour of our arrival at Penzance, he had disappeared, telling me not to wait up for him, as he could not say what time he would return. I accordingly went to bed early, for I was tired out, and had not seen him until now.

"I have been very busy, Sir John," he said. "In the characters of a mining engineer at one place and agent for a foreign shipping firm at another, I have been making some very necessary inquiries. I engaged a local motor—our own would hardly have suited the part—and I have covered a great deal of country."

"And your exact object?"

"I have two. One is to discover any private engineering works where special engines could have been made in secret. You will remember that we both came to the conclusion that the Air Pirate could have obtained silent engines in no other way. The other is—petrol."

"Petrol! I never thought of that! I see what you mean."

"Precisely, Sir John. An airship such as the one we are after must have a constant supply of petrol, and, of course, consumes enormous quantities. When I can connect a certain private individual with the receipt of such quantities, we are another step forward."

"How have you got on?" I asked eagerly.