His gaze fell on the can of radite. The wires leading to the interrupter fuse gleamed a dull gold with a malign significance. "If Carnes and I are both washed out, there will be only Thelma left. She can't fight Saranoff alone. Carnes knows the man and his methods. There is only one way that I can see to warn him out of the trap." He shuddered a moment. With a steady step he walked across the cave to the can of deadly explosive. A pair of pliers lay on a nearby bench. He picked them up. He dashed his hand across his face for a moment, but looked up with steady eyes. With hands that did not tremble, he bent down over the can. With a quick snip, he severed the wires leading to the can of radite. * * * * * Operative Carnes jumped ashore as the boat reached the bank of Bush River. Before him stretched a dismal swamp, interspersed with occasional bits of higher ground. He looked back over the river for a moment, taking his bearings with great care. A luminous lensatic compass gave him the orientation of the points he had chosen for markers. "Are you sure we are at the right place?" he asked in an undertone. "Sure as shootin', Mister," replied the boatman. "It's the only place of its kind in five miles. The rock you're hunting for is about a hundred rods due east." "It looks right," said Carnes. "Come on, men." Operatives Haggerty and Dillon scrambled out of the boat and stood by his side. "Follow me," said Carnes in a whisper. Both detectives nodded silently. They drew their pistols and fell in behind their leader. Keeping his direction with the aid of his compass, Carnes led the way forward, counting his steps. At five hundred he paused. "It should be right here," he whispered. Haggerty pointed in silence. In the starlight, a large rock loomed up a few yards away. With an exclamation of satisfaction, Carnes led the way to it. "Dig on the south side," he whispered, "and hurry! The damned thing is due to go off in less than twenty minutes. Unless we can find and cut the wire before then, the doctor is a gone gosling." The two detectives drew intrenching shovels from their pockets and dug feverishly. For five minutes they labored. Dillon gave an exclamation. "Here it is, Chief!" he said. Carnes bent down and ventured a short flash from a carefully guarded light. The detective's shovel had unearthed a powerful cable running through the earth. "Get something to cut on!" cried Carnes. Haggerty lifted a rock which they had unearthed and thrown to one side. Carnes raised the cable and laid it on the rock. "Now for your ax, Dillon!" he exclaimed. He turned on his flashlight. Dillon raised a hand-ax and took careful aim. Sparks flew as the ax fell on the rock, severing the cable cleanly. Carnes rose to his feet. "The doctor's safe!" he cried. * * * * *