Abbot did so. Out into the lock they sped, in the face of the surging current. Then Abbot pushed another button to close the gates behind them. But the water continued to fall, and they grounded before they reached the end of the lock. Quite evidently the rush of the current had kept the doors from closing behind them. The city was being flooded through the broken door of the storeroom. But Abbot opened the next gate, and again they breasted the incoming torrent. This time, although the level continued to fall, their craft did not quite ground. "They must have got the gates shut behind us at last," said he, as he opened the next set and pressed on. * * * * * And then he had an idea. Why not omit to close any further gates behind him? As a result, the sea pressure would eventually break down the inmost barriers, and destroy the city as effectively as Dolf's bomb would have done. But he said nothing to Milli of this plan: she might wish to save her people. Gate after gate they passed. This was too simple. A few more locks and they would be out in open water. The submarine of Hakin and Romehl swept by--evidently to let George and Milli know their presence--and then dropped behind again. But was it their two friends after all? It might have been some enemy! They could not be sure. This uncertainty cast a chill of apprehension over them, which was immediately heightened by the sudden extinguishing of the overhead lights of the tunnel. Abbot pressed the radio button for the next set of locks, but they did not budge. "What can be the matter?" he asked frantically. "My people must have turned off the electric current," Milli replied. "The gates won't open without electricity to feed the motors. We're trapped again." For a moment they lay stunned by a realization that their escape was blocked. "Kiss me good-by, dear," breathed Milli. "This is the end." As the young man reached over to take her in his arms, the submarine was suddenly lifted up and spun backward, end over end: then tumbled and bumped along, as though it were a chip on an angry mountain torrent. Stunned and bruised and bleeding, the young American finally lost consciousness.... * * * * * When he came to his senses again, his first words were, "Milli, where are you?" "My darling!" breathed a voice at his side. "Are you all right?" "Yes," he replied. "Where are we? What has happened?" "The entire system of locks must have crashed in and flooded the city," said she. Instantly Abbott's mind grasped the explanation of this occurrence: their leaving open so many gates behind them had made it impossible for the few remaining gates ahead to withstand the terrific pressures of the ocean depths, and they had crumpled. But he did not tell Milli his part in this.