The jungle humidity dragged on them, imparting a lethargy to the two men that reduced the speed and enthusiasm of their poling to a minimum. Regular dipping of their heads in the slow-moving water did little to cool them, and there was constant danger of emerging with some river parasite stuck to their face. They forgot that this part of the river ran through the range of an especially hostile group. The heat made it hard to think. They were still many miles from their destination when the lead man tottered for a moment, then fell headlong into the water.