Back went the fighting men of the great Revolution. back at the machine-guns, mounted in the breached walls. Gabriel was caught and whirled along in that living tide. He found himself at its crest, its foremost wave. Behind him, a roaring, rushing river of men. Before the Inner Citadel. Gathering speed and weight as it rolled up, the wave broke like an ocean surge over a crumbling dyke. Down went the Air Trust gunners and the guns, down, down to annihilation! Through the breach, foaming and swelling with irresistible power burst the tides of victory. Silenced now were the Trust guns. The steam-jets had none to man them. Far aloft, a last explosion told the death story of the final _épervier_. Here and there, from windows and corners of the wrecked and blazing plant, a little intermittent firing still continued; but now the hearts of these Air Trust defenders--scabs, thugs and scourings of the slum--had turned to water, in face of the triumphant army of the working class. They fled, those mercenaries, and all the ways and inner strongholds--such as still were left--now lay open to Gabriel and his comrades. Lighted by the blazing buildings and the vast fire torch of an oxygen-tank off to eastward, they stormed the final citadel, the steel and concrete laboratories, heart and soul and center of the hellish world-conspiracy. Stormed it, as it began to blaze and crumble; stormed it, in search of Flint and Waldron, would-be murderers of the world. Stormed it, only to see Herzog gnash his teeth upon the flask, and fall, and die; only to know that there, within the rock-hewn, steel-lined tanks, below, their enemies had still outwitted them! The swift onrush of the fire drove the victors back. "_Out, comrades! Out of here_!" shouted Gabriel, facing the attackers. None too soon. Hardly had they beaten a retreat, back into the vast courtyard again, strewn with the dead, when a second oxygen tank exploded, overwhelming the laboratory building with tons of flying steel. Leaping toward the zenith, a giant tongue of flame roared heavenward. So intense the heat had now become, that the solid brick and concrete walls, exposed to the direct verberation of the flame, began to crack and crumble. Gabriel ordered a general retreat of the attacking army. Victory was won; and to stay near that gushing tornado of flame, with new explosions bound to occur as the other oxygen tanks let go, must mean annihilation. So the triumphant Army of the Proletaire fell back and back still further, out into the wrecked and trampled Park, and all through the city, where shattered buildings, many of them ablaze, and broken trees, dead bodies, smashed ordnance and chaos absolute told something of the story of that brief but terrible war.