It was at the instant of Mistak’s triumph that a rifle shot rang out and one of Mistak’s men threw up his hands and fell silently to the ice. The half-breed Eskimo staggered back, his face paling, and his mouth twisted in a hideous smile.
Again the hidden rifle cracked, accompanied by another, whereupon Mistak’s men ducked and ran under the deadly bullets raining about them, leaving the boys where they had been captured.
“To zee pit!” the boys heard Mistak shriek to his men. “Kill zee policeman before zey come!”
Mistak and his men disappeared, and almost upon their heels leaped the two fur-clad forms of Corporal McCarthy and Constable Sloan.
In a trice they had slashed the bonds of the boys and had set them free.
“After Mistak all of you!” cried Corporal McCarthy, plunging on across the ice after the fleeing outlaws.
Dick kept pace with the Corporal and shouted into his ear: “Mistak is going to kill Corporal Thalman. He’s making for the pit now. You were just in time!”
“We came as fast as we could get here as soon as we got back to camp and found the map and instructions,” panted the policeman. “Good work you fellows have done!”
Just then the fleeing outlaws vanished into the yawning mouth of a cavern that led downward at a steep angle. Slipping and sliding most of the way, the policemen and the boys tumbled after them.
“Halt! Halt!” bellowed Corporal McCarthy when they had reached a more level incline. But Mistak’s men did not heed. Instead, the report of a rifle sounded like a thunder clap in the underground chamber and a bullet richochetted with a rattling noise along the walls of the cave.
“They’re shooting back at us!” cried Sandy.
In spite of the danger the policemen led the way on at a reckless run. Down, down, they went through the dimly lighted corridors of a subterranean vault. When it seemed to them they had gone down for nearly five hundred feet, the cavern swiftly became level and lighter.
“We’re going to run into the bottom of the fissure now!” panted Dick hoarsely.
Dick was right. The light grew stronger swiftly and a moment later they saw Mistak and his three men silhouetted in an opening as they ran out of the cavern.
Presently they burst out upon the frozen floor of a narrow canyon-like passage that was apparently the bottom of the fissure. Far above the sky showed like a tiny, pale ribbon. They could hear the sound of the running outlaws’ boots on the hard surface of the bottom of the fissure and followed them to the right. The passage was crooked and they could see nothing ahead of them further than ten yards, but at length they came upon the scene of Mistak’s contemplated perfidy.