Above the hissing of the rain Hythe could distinguish the deep purr of a powerful motor. Could it be that the "Vorwartz" was returning? If so, escape was impossible, for no cover of any sort was obtainable, and long before the whaler could return to the "Aphrodite" she would be overtaken by the swiftly moving submarine. "It’s that brute of a von Harburg coming downstream, sir," exclaimed Carclew. "We’re fairly trapped." In reply the sub ordered the boat to be turned and her head pointed down stream. Drawing the three detonating rockets from a locker under the stern sheets he rapidly lashed the sticks in position. Happen what may the "Aphrodite" must have warning of her enemy’s approach. Perhaps, as the "Vorwartz" was now under way her electrical current would operate the detector onboard the "Aphrodite"; if so there was every reason to suppose that Captain Restronguet was already on his way to rescue his whaler’s crew and engage his sworn foe. A chance of safety yet remained. "Give way, men," ordered Hythe. "We may do it yet." Nearer and nearer came the throb of the powerful motors. Hythe grasped the lanyard of the nearest rocket. He hesitated. There was something in the sound of the motors that could not be associated with a submarine, even allowing for the conductive properties of the water; it was more like the drone of an aerial propeller. The next instant the snub nose of a large airship appeared round the bend of the river. The vessel was flying low; her two suspended cars were not forty feet above the surface. Her yellow silk envelope was literally streaming as the rain descended upon it in torrents, and this was why, Hythe reasoned, she was flying so low. The sub ordered the whaler’s crew to cease rowing and soon the airship was overhead. Her engines were reversed, and losing way she brought up just in front of the boat. Hythe saw with feelings of relief that aft the airship was flying a Blue Ensign with a yellow propeller--the badge of the recently constituted British Empire Aero-League--emblazoned on the flag. Half a dozen men were leaning over the rail of the platform connecting the two cars. "What boat is that?" hailed a tall, sparsely-built man dressed in a white uniform. "The ’Aphrodite’ submarine, Captain John Restronguet," replied Hythe without hesitation. "What airship is that?" "The ’Pride of Rhodesia,’ of Salisbury. Is Captain Restronguet in the boat?" "No," replied Hythe. "He is on board the ’Aphrodite’ lying at the junction of this river with the Zambesi." "And who are you, sir, might I ask?" "Arnold Hythe, Sub-lieutenant of the Royal Navy." "So you are the Mr. Hythe we’ve heard so much about? Glad to meet you. Sorry we can’t shake hands; must delay that honour till a more convenient time. I’m Jones of Salisbury, Rhodesia, and we’re having a chip-in with that villain, Karl von Harburg. I suppose we are not too late?"