"I cannot think unless he has hidden it and will only give it up as the price of his liberty." "But if he keeps us down here, he will die, too." "He is playing his life against ours and he holds the cards." "Not for long. Come below at once. We must act quickly. There is a chance he still has it on his person." Down the stairs they ran, leaving Merritt at the wheel with a sinking feeling of fear clutching at his heart. If Barton, turned desperate, had hidden the key and would not reveal its hiding place, it meant that they must remain in the depths till death put an end to their sufferings. In the meantime, the ensign and Mr. Barr, both excited, had rushed through the cabin and toward the engine room. As they approached the door, it was slammed and a pistol thrust through a small hole in it, which had been cut for ventilation. Then Barton's voice came ringing out: "Don't come a step closer unless you want to get a bullet in you." "What's the matter, man, are you mad?" exclaimed Mr. Barr. A shriek of demoniacal laughter was the sole response. It sent a shudder through everyone who heard it. The man was mad, violently insane. The seeds of lunacy, which had been germinating in his brain for a long time, had burst forth into a terrible harvest. "And on that man everyone of our lives depends," breathed the ensign. Then in a louder tone, which rang with authority: "Barton, did you take that ascending lever?" "Yes; ha-ha-ha! It's a good joke on you! You thought you'd put me in prison, but now we'll all die together." "Barton," pleaded Mr. Barr, "be rational. Return that lever and you shall have immunity." "It's too late now!" screamed the demented wretch. "We'll all die together in the depths of the sea, where dead men's bones rot and the fish eat their eyes out." A hasty consultation followed between the ensign and Mr. Barr. The man was undoubtedly violently insane, and there didn't seem a chance in the world of dislodging him from his position. The situation was the more serious from the fact that the fresh air devices were not working properly and the air inside the submarine was already getting noticeably stale and foul. "We must rush that door; it's our only chance," declared the officer in a whispered voice. "But he is liable to shoot," objected Mr. Barr, eying the blued-steel muzzle of the revolver which was pointed threateningly at them. "It cannot be helped. It means death in a fearful form if we do not dislodge him from that position, and a man in his condition cannot listen to reason." "Well, what do you propose?" "That you start talking to him to distract his attention, offer him money or anything to give up the lever. Then I'll watch my chance and rush in on him; thank goodness, that door has no lock on it." "Barton!" said Mr. Barr, in a resonant voice. "Well?" snarled the lunatic. "Be calm now and listen to reason. Is it money you wish?" "No, blood! Human lives!" shrieked the maniac.