Gerald's shout for aid was drowned by the crash of the shattered timbers of the canoe, and ere he could repeat the cry the native had shifted the grip of his right hand to his antagonist's throat, while with his left he strove to wrench Tregarthen from the narrow platform. Realising that the moment he relaxed his grasp of the iron rail he was a lost man, Gerald contrived to strike out with his left. Handicapped by the fact that his hands were encased in thick woollen gloves, and that his reach was limited, the blow fell comparatively light. Then he tried to kick his antagonist clear, but at the first attempt the agile black, intent only on encompassing his enemy's destruction, twisted his legs in a crushing embrace round Gerald's waist, while both his sinewy hands were engaged in squeezing the sub-lieutenant's throat. Tregarthen felt his strength was ebbing, his breath came in quick gasps, and he gurgled in the throat under the relentless pressure. Even in those few moments of peril Gerald realised that once he fell into the sea the submarine would leave him to his fate, plunging onwards till those below could see that by her erratic course she lacked a guiding hand at the helm. By that time it would be too late. Held in the merciless grip, Gerald's range of vision was limited to the grey steel walls of the conning-tower two feet from his face. Even in the fierce, yet silent, struggle a slight dent in the metal wall exercised an unaccountable fascination till everything grew white and a filmy mist swam before his eyes. His hands were relaxing their hold, stronger came the succession of heaves as the savage sought to hasten the end. Flesh and blood could stand the strain no longer; the rail seemed to slip from his grasp, and with his antagonist still locked in an unyielding embrace he fell backwards. Weakened as he was Gerald braced himself to meet the shock of the icy-cold water, but with a jerk that almost broke his ankle he found his leg seized in a vice-like grip, while simultaneously the tenacious hold of the Patagonian was relaxed. He was dimly conscious of being unceremoniously hauled back to the platform of the submarine, and of Watson, one of the mechanics, making a sudden dart for the steering gear, a heavy spanner still grasped in his hand. Then everything became a blank. [Illustration: chapter XVIII] CHAPTER XVIII THE CAPTAIN'S REVENGE GERALD'S ruse had been successful. Knowing that the Indians of Patagonia frequently take prisoners any small parties of the crews of whaling vessels who allow themselves to be treacherously surprised, so as to plunder and afterwards hold them to ransom, he reasoned that the savages would remove their captives to their village directly the _Olive Branch_ had left the anchorage. Evidently the natives wished to keep the locality of their village a secret, and only Tregarthen's scouting instincts had given him the clue.