"And that secret aerodrome must be somewhere in Germany, hidden away in some out-of-the-way place," ventured Sharpe. "But in what part of Germany?" asked the commissioner. "Let me see," cried Keane, rising to his feet, and walking across the room to where the large map of Germany hung upon the wall--"why, it must be in the Schwarzwald!" "The Schwarzwald!" exclaimed the other two. "Yes, it is by far the best hiding-place in the whole country. One may tramp for days and never see a soul. It must be somewhere in the Schwarzwald." "Then to the Schwarzwald you must go to-morrow, adopting whatever disguises you desire, and you must find this hidden spot where the conspiracy has been hatched," concluded the colonel. *CHAPTER V* *THE AERIAL LINER* The airship liner, _Empress of India_, was preparing to leave her moorings, just outside the ancient city of Delhi, for Cairo and London. This mammoth airship was one of the finest vessels which sailed regularly from London, east and west, girdling the world, and linking up the British Empire along the All-Red Route. She had few passengers, as she carried an unusually heavy cargo of mails for Egypt and England, and a considerable amount of specie for the Bank of England. Several persons of note, however, figured amongst her saloon passengers, including the Maharajah of Bangapore, an Anglo-Indian judge, and a retired colonel of the Indian army. She was timed to depart at mid-day, and during the morning mailplanes had been arriving from every part of India with their cargoes of mail-bags, already sorted for the western trip. The great mammoth now rode easily with the wind, moored by three stout cables to the great tower which rose above the roof gardens of the air-station. An electric lift conveyed the passengers and mails to the summit of this lofty tower, from whence a covered-in gangway led to the long corridors which lined the interior of the rigid airship. "Have all the engines been tested?" the captain asks of the chief engineer, as he comes aboard with his navigating officer. "Yes, sir." "All the passengers aboard?" he asks next of the ground officer. "All except the maharajah, Captain, and I expect him any moment." "Excellent," replied the skipper. "There’s a good deal of bullion aboard from the Indian banks, I hear, and the rajah himself is likely touring a lot of valuables with him, I understand, as he is to attend several court functions at St. James’s Palace." "Yes, sir. I hope you won’t meet that aerial raider," replied the ground officer. "Poof! What can he do? He can’t board us in mid-air! Besides, I hear that the aerial police are on his track, and that all their fast scouts are patrolling the mail routes." "Yes, you’ll have an aerial escort with you for the first two hundred miles, Captain. They’ll pick you up shortly after you leave here."