There, lying in the Atlantic ooze, they found the shattered fragments of the _Sirius_, a transport which had disappeared about a month before. The great hull of the splendid vessel had been torn asunder by some explosive of tremendous power, and, more than this, her hold had been rifled of all its treasure and the most valuable portions of its cargo. After this there no longer remained any doubt that the depths of the ocean were the hunting-ground of some foe of society, one at least of whose objects was plunder. The President and Council of Aeria found themselves at last confronted and baffled by an enemy who could neither be seen nor reached in his hiding-place, wherever it might be, beneath the surface of the waters. Thousands of lives had been sacrificed, and treasure in millions had been lost by the end of the first year of what men had now come to call the New Terror. New fleets of submarine cruisers were built and held in readiness in all the great ports of the world, and these scoured the ocean depths in all directions with no further result than the swift and silent annihilation of vessel after vessel by some power which struck irresistibly out of the darkness and then vanished the moment that the blow had been delivered. As yet, however, no enemy appeared on land or in the air, nor were any tidings heard of the lost _Ithuriel_, or her captain and lieutenant. The Aerians had replaced her with ten almost identical vessels and had raised the strength of their navy to two hundred and fifty vessels, one hundred of which were kept in readiness in Aeria, while the other hundred and fifty were distributed in small squadrons at twenty-four stations, half of which were in the Western hemisphere and half in the Eastern. The submarine warfare had now practically ceased. Nearly two hundred vessels belonging to Aeria, Britain, and America, had been captured or destroyed by an enemy which at the period at which this portion of the narrative opens was as supreme throughout the realm of the waters as the Aerians were in the air. To the menace of the air-ships this hidden foe replied by severing all the oceanic cables and paralysing the communication of the world save overland and through the air. Thus, at the end of six years after the capture of the _Ithuriel_ by Olga Romanoff more than half the work of those who had brought peace on earth after the Armageddon of 1904 had been undone. All over the world, not even excepting in Aeria, men lived in a state of constant anxiety and apprehension, not knowing where or how their invisible enemy would strike them next. The Masters of the World were supreme no longer, for a new power had arisen which, within the limits of the seas, had proved itself stronger than they were. Communication between continent and continent had almost ceased, save where the Aerian air-ships were employed. In six short years the peace of the world had been destroyed and the stability of society shaken.