he implored the hermit. "Untie them!"
The s.h.a.ggy-haired man cast a terrified glance over 208 his shoulder, then bent over the scientist without speaking, his fingers fumbling with the rope. Frank and Joe and the two engineers looked on, hardly daring to breathe. It seemed too good to be true that help at last was at hand.
Frank"s mouth suddenly framed a warning-but too late. Klenger came striding swiftly into the cave and struck the hermit on the head with a slab of firewood.
The man of the mountain slid unconscious to the floor!
Klenger glanced at the rope which secured the scientist"s wrists, then gave a satisfied grunt and went out.
A moment later, the prisoners saw Klenger and Ben Stoper start up the shaft toward the top of the mountain.
"There they go," Joe said tensely. "Pretty soon Hawkins will follow them, and then-"
He broke off, but the others knew what he meant. Then their efforts would be useless.
Bob rolled his body toward the hermit, then sat up and, by twisting his bound wrists, managed to unscrew the cap of the canteen on his hip. He tilted the flask so that water splashed on Darby"s face.
The hermit stirred, and his eyelids fluttered weakly. Bob splashed his face again, then dribbled water into his wide-open mouth.
The hermit looked at him dazedly.
209 "You"ve done it, Bob!" Frank exclaimed excitedly.
Bob turned to the scientist. "Hurry, Dr. Foster," he said. "Make Tom untie these ropes!"
Within a few minutes the hermit had freed Dr. Foster"s hands and feet. Then the two men set io work on the others.
Soon, all the prisoners stood free.
"Come on, d.i.c.k!" Bob cried. "We"ve got to stop Hawkins before he seals the tunnel opening!"
"Suits me!" his a.s.sistant replied.
They raced through the cavern and into the lantern-lighted tunnel.
"We"ll follow Klenger and Stoper!" Joe yelled after them. He ran to the shaft which sloped toward the mountaintop. "Come on, Frank!"
"Joe-wait!"
Joe stopped, puzzled.
"We won"t gain anything by trying to overtake those men," Frank told the youth rapidly.
"Klenger"s got a gun!"
"But we can"t let them get away!" Joe pleaded.
"They won"t!" Frank promised.
He signaled to Dr. Foster and Tom Darby tc follow him and went quickly to the kiln.
Pointing toward the pile of green firewood, he directed: "Keep feeding the fire until you get up plenty of smoke, then bank it. We just want to feed Klenger and Stoper enough smoke to make them helpless," he said, "not suffocate them!"
210 The scientist nodded his understanding, and Joe"s face broke into a grin.
"We"ll give them a dose of the medicine they gave us!" he declared.
The two youths slipped on their gas masks which were still slung over their shoulders.
Joe grabbed a lantern. Then they started up the shaft after the two men.
They came upon Klenger and Stoper in the narrow fissure near the top of the crevice.
Smoke streamed through the narrow tunnel, and in the light of the lantern the boys Saw the men clutching at their throats as they gasped for air.
They quickly dragged the helpless pair through the opening in the mountaintop. Then, when they had disarmed them, the boys took off their masks.
"Look who"s coming!" cried Frank.
Climbing up the mountainside came Bob and d.i.c.k. And a few steps behind them came Chet and Fenton Hardy!
"Dad!" Frank exclaimed with delight when they reached the top of the trail. "When did you arrive on Skull Mountain?"
"Not long ago," Mr. Hardy said. "But not soon enough to give you and Joe much of a hand in capturing the Klenger gang, it appears."
"Don"t believe him," Bob told the boys. "When d.i.c.k and I got to the mouth of the tunnel, your dad already had Hawkins in handcuffs!"
211 "I left him at the foot of the hill in care of a couple of FBI men," Mr. Hardy explained. He turned to Klenger and Stoper. "The FBI especially wants you two," he told them, "for holding Dr. Foster against his will. Maybe you haven"t heard, but kidnaping is a Federal offense!
Your pals already are safe in jail!"
The two men stared at Mr. Hardy but said nothing.
"Hey!" Chet demanded. "Don"t I get any attention? I helped too, didn"t I?"
"You sure did!" Fenton Hardy laughed, throwing his arm around the boy. "Chet gave me your message," he told his sons, "and brought me to the camp. That"s how we discovered the tunnel was exposed."
Joe sighed. "Well, I guess this winds up another mystery," he said.
"Don"t take it so hard," Frank comforted him with a grin. "Another one will turn up soon!"
And although he did not realize it at the time, Frank was speaking the truth. For the Hardy boys were closer to the mystery of the "Sign of the Crooked Arrow" than they knew.
Now, standing on the crest of Skull Mountain, the boys, their father and their friends stared down at Tarnack Valley.
The scar which the rockslide had left on the mountainside stood out raw against the green of the 212 foliage. Soon it, too, would be covered with trees and bushes once more. But long before that, the mouth of the prehistoric tunnel would have been walled up forever. Then the thin sheet of water which now covered the valley would rise and become a deep lake.
Bob smiled happily as he pictured it.
"Teii the folks in Bayporl to start turning on their faucets," he told the Hardy boys with a grin. "From now on, tiiere"s going to be plenty of water for Sat.u.r.day baths!"