door, and the imperturbable Jones entered once more, and announced:

"Message from Keane and Sharpe came in whilst you were speaking on the telephone, sir."

"Good!" ejaculated Tempest, as he wiped the perspiration from his brow, for he had expected something much worse from the Home Secretary. "What does the message say?"

"They received my last message, sir, and are on their way home by the fastest aeroplane. They are due at Hounslow aerodrome at midnight."

"Excellent! What time is it now, Jones?"

"It wants ten minutes to midnight, sir, and I have sent out the fastest car to meet them and bring them straight here. They should be here in half an hour, sir."

"Have you told them at Hounslow?"

"Yes, sir, and they have already got out the coloured lights and the ground flares."

"You have done well, Jones, but you had better not leave the office to-night. I'm very sorry, but I may want you. This is urgent business; we're up against something this time, and unless Keane and Sharpe have found something out, we're going to be beaten."

"I'll stay, sir, but what about you? This is your third night-sitting, and you've had nothing since lunch. Shall I order supper for you?"

"Oh, thanks, Jones, but I'd forgotten. Yes, you may order me coffee and a sandwich, and get something for yourself. You're getting the strain as well, and I don't want you to break down."

When left alone, Colonel Tempest once more began to pace the soft-carpeted room, much as a captain paces the bridge when his thoughts are unduly disturbed by some untoward event during the watch of the second officer. Every other minute he consulted his watch, and wondered why the time passed so slowly. Twice he rang down to the lobby attendant and asked if Captain Keane had arrived, and twice the same answer was returned.

Then he looked at the maps on the wall, and followed with his finger the trail of the All-Red Route which the aerial liners followed, linking up the empire and half the world. Now and again he would glance shrewdly at the large map of Germany, as a skipper eyes the weather quarter when a storm is brewing. Occasionally he would murmur half aloud:--

"A silent engine ... three hundred miles an hour. Gee whiz! but they have beaten us two to one. We shall never catch them."

Then a slight sound caught his ears from outside the great building. The soft purr of an approaching Rolls-Royce motor and the sharp blast of a Klaxon horn followed.

"At last!" he cried. "Here they come!"