an oath, his hand raised to strike.He recovered himself and essayed a sickly smile.
"I will remember, Doctor," he said in a voice which, despite himself,had a tremor of fear in it. "I will remember--_when_ we meet again."
He ran lightly up the stairs and Dr. Bird heard the floor close abovehim. With a grunt, he bent down and examined his shackles closely.They were tight fitting and made of hardened steel. A cursoryexamination showed the doctor that he could neither force them norslip them. He turned his attention to the key which Saranoff hadpointed out. It lay on the floor, about ten feet, as nearly as hecould judge, from where he stood.
He knelt and then stretched himself out at full length on the floor.By straining to the uttermost, his groping fingers were still sixinches from the key. Saranoff had calculated the distance well.
Convinced that he could not reach the key by any effort of stretching,Dr. Bird wasted none of his precious time in vain regrets or inuseless efforts to accomplish the impossible. He rose to his feet andcalmly took stock of the room, searching for other means of freeinghimself. The shackles themselves offered no hope. He searched hispockets. The search yielded a pocket knife, a bunch of keys, aflashlight, a handkerchief, a handful of loose change, and a wallet.He examined the miscellany thoughtfully.
* * * * *
A light broke over his face. He tied one end of the handkerchief tothe knife and again took a prone position on the floor. Cautiously hetossed the knife out before him. It fell to one side of the key. Hedrew it back and tried again. The knife fell beyond the key. Slowly hedrew it back toward him by the handkerchief. When it reached his hand,he saw to his joy, that the key was a good inch nearer. With a lighterheart, he tried again.
His toss was good. The knife fell over the key, and again he drew itto him. To his disgust, the key had not moved. Again and again hetried it, but the knife slid over the key without moving it. He lookedmore carefully and saw that the key was caught on an obstruction inthe flooring.
With careful aim, he threw his knife so as to drive the key furtheraway. He threw the knife again and tried to draw the key to him fromits new position. It came readily until it reached the inequality inthe floor which had stopped it the first time. All of his efforts todraw it nearer were fruitless. He give vent to a muttered oath as helooked at the clock. Thirty minutes of his time had gone.
A second time he knocked the key away and strove to draw it to himwith no success. The clock bore witness to the fact that another tenminutes had been wasted. He rose to his feet and carefully surveyedhis surroundings.
A cry of joy burst from his lips. On the floor was a tiny metallicthread which he knew for a wire. He bent down and picked it up. It wasfine and very flexible. He doubled it three times and strove to bend ahook in it. The wire was too short to offer much hope, but he threwhimself prone and began to fish for the key.
The wire reached it readily enough, but it did not have rigidityenough to pull the key over the little bump which held it. A glance atthe clock threw him into an agony of despair. A full hour had passedsince Saranoff had left him. Carnes might even now be walking into thetrap which had been laid for him.
He rose to his feet and thought rapidly, twisting the wire idly aroundthe knife as he did so. He glanced at the work of his hands, and anoath broke from his lip.
"Fool!" he exclaimed. "I deserve to die! The means for liberation werein my hands all the time."
* * * * *
With feverish activity, he ripped open the flashlight. He held the twoends of the wire against the terminals of the light battery andtouched the knife to his steel key ring. To his joy, the ring adheredto the knife. Under the influence of the battery, the wire-wrappedknife had become a small electromagnet.
In a moment the doctor was prone on the floor. He tossed the knifeout to the key. His aim was good and it fell directly beyond. Withtrembling hands he drew the knife toward him. It reached the key.Scarcely daring to breathe, he pulled it closer. The key had risenover the ridge which had held it, and was adhering to the knife. Inanother moment, he stood erect, freed from the shackles which hadbound him.
He made for the door at a run, but a sudden thought stopped him. Theclock showed him that an hour and twenty minutes had passed.
"Carnes must be nearly here!" he cried. "If I go blundering out, I'mliable to run right into the trap they have laid for him, and thenwe're both gone. If I yell to warn him, the fool will come ahead atfull tilt. What the dickens can I do?"
His gaze fell on the can of radite. The wires leading to theinterrupter 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 tothe 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, hebent down over the can. With a quick snip, he severed the wiresleading to the can of radite.
* * * * *
Operative Carnes jumped ashore as the boat reached the bank of BushRiver. Before him stretched a dismal swamp, interspersed withoccasional bits of higher ground. He looked back over the river for amoment, taking his bearings with great care. A luminous lensaticcompass gave him the orientation of the points he had chosen formarkers.
"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 placeof its kind in five miles. The rock you're hunting for is about ahundred rods due east."
"It looks right," said Carnes. "Come on, men."
Operatives Haggerty and Dillon scrambled out of the boat and stood byhis side.
"Follow me," said Carnes in a whisper.
Both detectives nodded silently. They drew their pistols and fell inbehind their leader. Keeping his direction with the aid of hiscompass, Carnes led the way forward, counting his steps. At fivehundred he paused.
"It should be right here," he whispered.
Haggerty pointed in silence. In the starlight, a large rock loomed upa few yards away. With an exclamation of satisfaction, Carnes led theway to it.
"Dig on the south side," he whispered, "and hurry! The damned thing isdue to go off in less than twenty minutes. Unless we can find and cutthe wire before then, the doctor is a gone gosling."
The two detectives drew intrenching shovels from their pockets and dugfeverishly. 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 guardedlight. The detective's shovel had unearthed a powerful cable runningthrough the earth.
"Get something to cut on!" cried Carnes.
Haggerty lifted a rock which they had unearthed and thrown to oneside. 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 carefulaim. Sparks flew as the ax fell on the rock, severing the cablecleanly. Carnes rose to his feet.
"The doctor's safe!" he cried.
* * * * *
He started at a run toward the north. He had gone only a few feet whena beam of light flashed across the marsh, picking him out of thedarkness. He paused in amazement.
A flash of orange light stabbed the darkness and a heavy pistol bulletsang past his head. The detective raised his weapon to reply, butthree more flashes from the darkness were followed by the viciouscracks of large caliber automatics.
"Down, Chief!" cried Haggerty.
Carnes dropped to the ground, the beam of light following hismovements. Four more flashes came from the darkness. Mud was thrown upinto his face. Dillon's
gun joined Haggerty's in barking defiance intothe night.
A groan came from Haggerty.
"Hit, Tom?" asked Carnes anxiously.
"A little, but don't let that bother you. Get that damned light!"
He fired again, groaning at he did so. There was a crash from over themarsh and the light went out.
"Good work, Tom!" cried Carnes.
He raised his pistol and fired again and again into the darkness, fromwhich still came the flashes of orange light. A cry of pain rewardedhim.
"Come on, men, rush them!" he cried.
He jumped to his feet and dashed forward. A fresh beam of lightstabbed a path through the darkness. A volley of fire came from behindit. Haggerty stumbled and fell.
"They've got me, Chief!" he cried faintly.
Disregarding the storm of bullets, Carnes charged ahead, Dillon at hisheels. A sudden shout came from his left. A