"He is our unconscious ally. He will kill off a good many of his comrades for us. But I will not mystify you any longer. Why did he fall off the rigging--because he was awkward, as Duval said? Not a bit of it. He fell because he was dizzy. Why was he dizzy? Because he was ill. This afternoon, when I saw him first, I more than suspected that a fall could not account for all his symptoms. I have just examined him again. I know the signs well. He is in the first stage of _yellow fever_!" "Yellow fever?" "Yes, yellow fever has come to help us. The man has been very sick and is now delirious. The stupid captain has seen him, and puts it all down to his fall; says he must have injured his spine. How lucky for us was that fall! Led off the scent by it, the idiots will not suspect what is the matter with the man until the _vomito negro_ declares itself. They have not separated him from the rest. He is now lying in his bunk in the forecastle. All the watch below are sleeping round him. It is a small forecastle, and the crew, imagining that fresh air is bad for a sick man, have closed the ports. It is stifling down there at present. It is a pest-house. All those men are breathing in contagion. Do you know that it is the worst form of yellow fever that is now raging at Rio--very contagious, very fatal? If it breaks out in a vessel like this it will spread like wildfire. Man after man will fall sick and die." "Ourselves included," said Carew recklessly. "No, sir. We will take precautions in time. I have had the fever once, and am not likely to have it again. I have hinted the truth to El Chico and El Toro, and they have suddenly developed a hygienic craze for fresh air, and insist on sleeping on deck to-night, to the amazement of the French sailors. I would not like to insure the lives of the men who sleep in that forecastle; most of them are doomed by this time." Carew felt his skin turn cold and tingle with horror as he listened to the Frenchman's cold-blooded exultation in the dreadful prospect. "Good-night, captain. I am going to turn in now; and, by the way, let me advise you to keep on deck in the cool wind as much as possible, and smoke perpetually. Tobacco is a splendid disinfectant." CHAPTER XIII On the day after the crew of the _Petrel_ had been taken on board the barque the wind freshened and was so much to the south of east that the vessel was enabled to sail in a north-easterly direction, a course which would bring her to the vicinity of the Trinidad and Martin Vas Archipelago. When Carew came on deck in the morning he found Baptiste there before him. The Provençal walked up to him jauntily, twirling his long black moustache, and looking jubilant. "I have seen young Hallé again," he said, in a low voice. "He is very bad. The symptoms are unmistakable; but no one suspects the truth so far. Two other men are complaining of headache." "Let the accursed plague work its way," said Carew gloomily, "but tell me nothing about it."