It was not the first time they had heard that voice calling since they had ventured deep into the unpeopled swampland about which the downriver settlements had fearful stories to whisper. Silently the guide spun the engine. The boat sputtered on. Dalton strained his eyes, watching the darkening shore as he had watched fruitlessly for so many miles. But now, as they rounded a gentle bend, he glimpsed a small reddish spark near the bank. Then, by the last glimmer of the swiftly fading twilight, he made out a boat pulled up under gnarled tree-roots. That was all he could see but the movement of the red spark told him a man was sitting in the boat, smoking a cigarette. "In there," he ordered in a low voice but Joao had seen already and was steering toward the shore. The cigarette arched into the water and hissed out and they heard a scuffling and lap of water as the other boat swayed, which meant that the man in it had stood up. He sprang into visibility as a flashlight in Dalton's hand went on. A squat, swarthy man with rugged features, a _caboclo_, of white and Indian blood. He blinked expressionlessly at the light. "Where is the American scientist?" demanded Dalton in Portuguese. "_Quem sabe? Foi-se._" "Which way did he go?" "_Nao importa. O doutor e doido; nao ha-de-voltar_," said the man suddenly. "It doesn't matter. The doctor is crazy--he won't come back." "Answer me, damn it! Which way?" The _caboclo_ jerked his shoulders nervously and pointed. "Come on!" said Dalton and scrambled ashore even as Joao was stopping the motor and making the boat fast beside the other. "He's gone in after it!" The forest was a black labyrinth. Its tangled darkness seemed to drink up the beam of the powerful flashlight Dalton had brought, its uneasy rustlings and animal-noises pressed in to swallow the sound of human movements for which he strained his ears, fearing to call out. He pushed forward recklessly, carried on by a sort of inertia of determination; behind him Joao followed, though he moved woodenly and muttered prayers under his breath. Then somewhere very near a great voice croaked briefly and was silent--so close that it poured a wave of faintness over the hearer, seemed to send numbing electricity tingling along his motor nerves. Joao dropped to his knees and flung both arms about a tree-bole. His brown face when the light fell on it was shiny with sweat, his eyes dilated and blind-looking. Dalton slammed the heel of his hand against the man's shoulder and got no response save for a tightening of the grip on the treetrunk, and a pitiful whimper, "_Assombra-me_--it overshadows me!"