The moon was shedding a cold radiance around, in strange contrast with the hot and sultry air, when the airship with its three passengers rose from the foot of the hill and started on its voyage for the kasbah of Ain Afroo. To lessen the chances of premature discovery, Tom ascended to a considerable altitude, with the intention of dropping obliquely upon the kasbah. He was thus able to dispense in great part with the action of the propellers as the airship drew near to its destination, which was very desirable, seeing that they made a loud whirring which must otherwise have attracted attention. But by ascending to a height of nearly 3,000 feet, and then adjusting the planes so that the airship fell at a sharp angle, he could make use of the force of gravity to carry him in the right direction without employing the horizontal screws. Finding, however, when half the distance had been covered, that the airship was coming too near the ground, he set the vertical screws in motion rose a few hundred feet, and again dropped obliquely towards his objective. The whole country was bathed in the moon’s pale light, and lay in perfect silence save for the faint barking of dogs here and there. The three adventurers said never a word; neither Tom nor Oliphant was in a mood for talking now that the real business of the expedition was so near at hand. It was not until the airship was hovering exactly over the flat roof of the kasbah that they knew, from shouts below, that the strange visitant had been observed. But some moments must elapse, presumably, before the alarm could penetrate to the sheikh’s apartments; and, aware that everything depended on his coolness and caution, Tom brought the airship to rest with as much deliberation as if he were landing from a practice voyage. A shot from a musket struck one of the planes. “The sentry on the terrace has caught sight of us,” said Tom, as he was stepping out of the car. “Let us hope that after having done his duty he’ll be sufficiently scared to bolt for the town, instead of coming up to warn the sheikh.” The programme had been settled before they started. Oliphant was to remain in charge of the airship, while Tom and the Moor attempted to get into the house and release the prisoner. “Remain in the car,” said Tom, “and have everything ready to ascend at a moment’s notice.” “Wish you good luck, old fellow,” returned Oliphant. “You’ve got your revolver?” “Yes. _Au revoir!_”