the stain. He found a steward hesitating outside the door of Ortiz's cabin. He touched Bell's arm anxiously as he was about to go in.
"Beg pardon, sir," he said, and stammered. "I—I heard Mr. Ortiz making some—very strange noises, sir. I—I thought he was sick. . . ."
"He is," said Bell grimly. "He told me he does not want a doctor, though. I'm looking after him."
He closed the door behind him, and Ortiz grinned at him. It was a horrible, a terrible grin, and Ortiz fought it from his face with a terrific effort of will. There was foam about his lips.
"DIOS! It was—it was devilish!" he gasped. "Senor Bell, amigo mio, for the love of the good God get my revolver from my trunk. Give it to me. . . ."
Bell said shortly: "The airplane just radioed that it's going to try to swoop overhead and drop a package on board the steamer. It doesn't dare alight in this fog."
"I think," gasped Ortiz, "I think it would be well to tie my feet. Tie them fast! If—if the package comes, if I—if I am unpleasant, knock me unconscious and pour it into my mouth. I fear it is too late now. But try it. . . ."
Through the port came the muttering of a seaplane's engines. The noise died away. Almost instantly the siren boomed hoarsely.
"Ah, Dios!" said Ortiz unsteadily. "There it is! Senor Bell, I think it is too late. Would you—would you assist me to go out on deck, where I might fling myself overboard? I—think I can control my legs so long."
"Steady!" said Bell, wrenched by the sight of the man before him fighting against unnameable horror. "Tell me—"
"It is poison," said Ortiz, his features fixed in a terrible effort of will. "A ghastly, a horrible poison of the Indios of Matto Grosso, in Brazil. It drives a man mad, murder mad. It is as if he were possessed by a devil. His hands first refuse to obey him. His feet next. And then his body. It is as if a devil had seized hold of his body and carried it about doing murder with it. A part of the brain is driven insane, and a man goes about shrieking with the horror of what crimes his body commits until the poison reaches that portion of his brain as well. Then he is mad forever. That is what I face, amigo mio. That is why I beg you, I implore you, to kill me or assist me, to the side of the ship so that I may fling myself overboard! The Master had it administered to me secretly, and demanded treason as the price of the antidote. He deman—"
STEADY and strong, rising from a muttering to a steady roar, the sound of airplane motors came through the port. Bell started up.
"Hold fast," he snapped savagely. "I'll go get that package when it lands. Hold fast, I tell you! Fight it!"
He flung out of the cabin and raced up the stairs. The door to the deck was open. He crowded through a group of passengers who had discounted the dampness for the sake of a novelty—an airplane far out at sea—and raced up to the upper deck. The roaring noise was receding. The siren roared hoarsely. Then the noise came back.
For minutes, then, the ship seemed to play hide-and-seek with the invisible fliers. The roaring noise overhead circled about, now near, now seeming very far away. And the siren Bent its dismal blasts out into the grayness all about. Then, for an instant, a swiftly scudding shadow was visible overhead. It banked steeply and vanished, and seemed to have turned and come lower when it reappeared a moment later. It was not distinct, at first. It was merely a silhouette of darker gray against the all-enveloping mist. But its edges sharpened and became clear. One could make out struts, an aileron's trailing edge
