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.