They halted in a little clearing to complete their interrupted task of donning their clothes. With their ears strained to catch the faintest suspicious sound, they struggled into their light cotton garments, that at the best of times were ill-adapted to the miasmic night-mists of the East African coast. "That's better," exclaimed Denbigh cheerfully. "Feel a bit more civilized. We might pass muster as a pair of Christy minstrels. Now, then, a few grains of quinine, and we'll be on the move." O'Hara's reply was to release the safety-pin of his automatic pistol. Denbigh, who was studying the luminous face of the pocket-compass, smiled grimly. "Now I'll admit that little toy may come in handy, old man," he remarked. "Since I lead the way, pray be careful how you finger the trigger. Nor'east by east is the ticket." Before the adventurers had proceeded fifty yards, a rustling sound overhead brought them up all-standing. Some heavy body was moving from tree-top to tree-top with great rapidity. "Doesn't sound very healthy," whispered Denbigh with a forced laugh. "I think I'll arm myself with a club." He wrenched at a stout sapling. Instead of the stem coming out by the roots as he expected, it snapped off short. The fractured part tapered to a chisel edge. The wood was hard and close-grained. "No, I'll use this as a spear," continued the sub. "It makes a nasty weapon to jab an animal with." In silence the chums proceeded on their way. It was fair going between the trunks of the palms and mangroves, there being very little undergrowth. "'Ware mosquitoes," exclaimed O'Hara. "There must be a swamp somewhere about." A swarm of these pestilential insects were buzzing around their heads, but, possibly owing to the protection afforded by the burnt cork, the mosquitoes did not press home the attack. Fifty yards farther the two men were stopped by a deep morass. "Edge away to the left," suggested the Irishman. "I think I can hear running water. By Jove! Look at those fireflies. They're simply great." Denbigh merely grunted. He was in no mood to study the beauties of nature. The marsh meant loss of valuable time. Half a dozen small deer, disturbed in the act of drinking, came bounding towards them, until, finding themselves confronted by human beings, they stopped abruptly, then tore madly from the newest danger. "Be careful!" urged Denbigh. "Those creatures have been driven towards us by some animal. Stand by." Out of the deep shade ambled a huge unwieldy figure. It looked like a giant armed with a club. It was too big for a native: it was an enormous ape. In a trice Denbigh and his companion dodged behind a tree; but quick though they were, the movement had not escaped the notice of the animal. Uttering a shrill cry, the ape bounded towards their place of concealment.