“Seems more like a threat than a warning to me,” Haverly rejoined. “I guess they’d hardly hang a message up that all the wolfish freaks in the underworld could see, if they intended to warn us. No pard, you take----” A screech awoke the echoes of the underworld; there was a whirring of mighty wings, and out of the gloom swooped a monstrous black shape, swift and terrible. Seymour was knocked sprawling to the ground as the creature flashed past him and vanished again into the darkness whence it had emerged. The millionaire stared in amazement, then, as his friend rose, he found voice. “I guess that’s the biggest bat I ever struck!” “Bat!” ejaculated Seymour, “you don’t mean to say that was a bat?” “It was nothing more or less,” retorted Silas; “but here he comes again; now’s your chance to get your own back.” Simultaneously the two men pulled trigger, and the huge creature swooping down upon them, flapped wildly for a moment, then sank heavily to earth, beating the ground madly with its mighty wings. Its eyes glared savagely at the two comrades, and it made a futile effort to drag itself towards them, seeming to know that they were the cause of its injury. Half a dozen shots they fired into the great body ere the creature lay still; then, when all movements of the wings had ceased, they moved forward to examine the carcase. It was, as Haverly had said, a gigantic bat or vampire, armed with hyaena-like teeth and great curved claws that made it a terrible enemy. Its membranous wings, outstretched, could not have been less than fifteen feet from tip to tip, and it would apparently have had little difficulty in carrying off either of the comrades had it succeeded in gripping one of them at its first swoop. “What hideous monsters this underworld contains!” exclaimed the baronet disgustedly, as they pushed on once more. “Mervyn would be in raptures could he see that brute. Anything new or strange attracts him like a magnet.” “I reckon we’ll have to flicker if we’re to save him and Garth,” returned Silas shortly, and increased his pace. Pressing forward with redoubled speed, every nerve and muscle strained to the utmost, they reached the glade. A brief rest, then on again until they emerged upon the beach, off which they had left their vessel. Eagerly they looked for the welcome gleam of the searchlight. But they looked in vain. _The “Seal” had vanished!_ A despairing cry burst from the baronet as this fresh misfortune became apparent. What hope was there for Garth and Mervyn? What chance of their ultimate rescue now? Even Haverly grew depressed as he thought of the issues at stake. It seemed as though fate itself were against them. That now, while their comrades’ lives were perhaps trembling in the balance, the vessel, upon whose aid they had relied, should fail them, was a blow indeed.