“Olga inherited from her grandfather, the father of the Vladimir Romanoff who was executed for disobeying the order of the Council, all the plans and directions necessary for the building both of air-ships and submarine vessels, and as soon as this perfect stronghold and hiding-place was discovered, her accomplices in the conspiracy for the restoration of the Russian monarchy at once devoted their fortunes to the supply of money and materials. The _Revenge_ made one more voyage to Russia, and by travelling at full speed at a great elevation managed to make it unobserved. “The services of the cleverest engineers and most skilful craftsmen among the revolutionists were secured. Transports were chartered and sent out to Antarctica loaded with materials. On the shores of the subterranean lake the first squadron of submarine vessels was built, and then began the system of ocean terrorism which soon paralysed the trade of the world. “Piracy was carried on with utter ruthlessness. Transports were sunk by the vessels, and then plundered by divers of the treasure which they carried, and which was employed to purchase new materials and to repay those who had furnished the first funds. “Alexis and myself were kept by Olga, as I said in my first letter, under the influence of a drug which completely paralysed our volitional power, and were compelled to reveal all we knew concerning our own air-ships, submarine vessels, guns, and explosives. And in this manner was created and equipped the force which will be employed to dispute with us the empire of the world unless we are able to extirpate it utterly.” While the despatch to the Council was being drawn up, the _Narwhal_ had been lying in the inner basin of Christmas Harbour, renewing her store of motive power from the generating station ashore. As soon as the engineer in charge reported that her power-reservoirs were full, and Alan had delivered the despatch for conveyance to Aeria by air-ship, Alexis, who had been apparently buried in a brown study for the last two hours or so, asked Alan to come with him into his private cabin, and as soon as the two friends were alone together he said to him-- “Look here, old man! While you fellows have been drawing up that despatch, and talking about the impossibility of attacking the stronghold at Mount Terror, I’ve been doing some thinking, and I’ve come to the conclusion that as far as an under-sea attack is concerned, it isn’t quite so hopeless as you’ve made out.” “I shall be only too delighted to hear you prove us wrong,” replied Alan, his eyes brightening at the prospect, for he knew Alexis too well not to be sure that he would not have spoken in this way unless he had pretty solid reasons for doing so. “Say on, my friend; I am all attention.” “Get out to sea, then, as fast as ever you can,” said Alexis, “for there’s not an hour to be lost if you adopt my plan, and if you don’t we can just come back.” “Very well,” said Alan. “What’s the course?”