"Maybe something's hidden behind the timbers!" Joe conjectured excitedly.
Frank doubted this. "These shorings look as if they've been here forever."
"Let's make sure," Joe urged. "We'll want to take the crowbar along with us, anyhow, so we can check it for clues. Hold my flashlight, will you?"
Gripping the handle carefully, so that at least part of the surface could be tested later for fingerprints, Joe yanked hard on the crowbar. It gave scarcely at all. He threw his whole weight into the effort and began forcing the bar from side to side. The timbering creaked ominously. I "Hey, be careful!" Frank warned.
"This tunnel isn't shored up too solidly along here!"
"Don't worry-I can get the bar out." Joe grunted, heaving hard. "It's coming now!"
The rotten wood crumpled and shredded as the crowbar gouged into it. Suddenly, as Joe gave one last hard yank, there was a loud splintering noise. The ceiling sagged.
"Look out!" Frank cried out. He grabbed Joe's arm, and both boys leaped ahead in the nick of time.
A split second later the tunnel caved in! As the boys dashed to safety, tons of earth and rock came pouring down. The passageway rumbled and thundered with the deafening impact.
"Good grief!" Joe stared back in awe after he and his brother had come to a halt deeper inside the tunnel.
"I should have listened to your warning, Frank!"
"Forget it. Let's be thankful neither of us got hurt and that I still have our flashlights."
Both boys coughed and tried to screen their noses from the cloud of dust billowing through the passage.
Gradually the particles settled.
"How do we get out of here?" Joe asked worriedly. "Dig our way through?"
The brothers strode back toward the scene of the cave-in. The tunnel there was totally blocked by the tremendous fall of dirt and rock.
"What about the crowbar?" Frank asked suddenly. "We can use that."
"I dropped it," Joe admitted, red-faced. "It's somewhere underneath all this rubble."
"Oh, great."
"Maybe we can still dig through," Joe said. "Come on-let's try!"
The Hardys set their flashlights on the ground, then began clawing away the debris with their hands. Soon the boys were panting and soaked with perspiration. In addition to loose dirt and stones, huge hunks of rock had broken off and been carried downward in the cave-in.
After trying vainly to shift one enormous stone fragment, Frank and Joe gave up in despair.
"We'll never make it," Frank said, breathing hard. "We don't even know how far the cave-in extends."
Joe leaned against the wall to collect his strength. "That means we'll have to find another way out of here."
"If there is one."
Although neither boy said so aloud, they knew their situation was desperate. Brady's Mine was only one of the places on Hank's map which they had picked out to search and they had told no one of the clue they had overheard. No doubt a search party would be organized when they failed to return. But how long would they be trapped underground before help might arrive?
"No use standing here," Frank said finally. "Let's find out where the tunnel leads."
"Right. We're getting fresh air, so there must be an exit."
Using only one flashlight in order to conserve their battery power, the Hardys pressed on.
"Joe, there's another reason why we'll find an exit," Frank said suddenly. "I believe someone from the gang was doing that tapping. If so, he must have been on this side of the cave-in."
"Sure-and the noises we heard were the sounds of the crowbar being pounded into position," Joe guessed.
"Let's hope he hasn't heard us," Frank murmured. "And the chances are there was more than one member of the gang here."
"Probably they scooted out the other entrance, so they wouldn't be caught in the cave-in," Joe reasoned.
"But we'd better talk in whispers just the same."
Both boys realized also that the flashlight beam would make them easy targets. But they had no choice.
Without a light to guide them, there would be no hope of finding a way out through the inky darkness.
Presently the tunnel widened, opening into a sizable cavern. The Hardys held their breath as Frank swept his flashlight beam rapidly about the chamber. He and Joe were ready to dive to the floor or retreat at the first sign of an enemy. But the cavern was empty.
"Look!" Frank exclaimed. "Another tunnel!" He aimed his light toward a dark hole that gaped in the far wall.
The two boys hurried to examine it. This passageway was narrower than the one they had just left and not shored by timbers. It was high enough for the Hardys to walk erect, but in places they found it a tight squeeze.
This time, Joe took the lead. Although the tunnel twisted and turned, he pressed forward steadily. He became aware that the cool draft was growing stronger.
"Feel the breeze?" Joe called back over his shoulder. "We must be near the end."
Joe had spoken too soon. They turned a sharp corner and the tunnel ended in a sheer wall of solid rock.
They could go no farther!
The boys shone their flashlights upward. There was nothing to see but the rock roof.
Joe gave a groan and sank down on the rocky floor of the tunnel. "What'll we do now?"
For a few minutes the brothers sat in silence. Then suddenly Frank leaped to his feet. "The draft!" he said.
"What about it?"
"We've passed the opening."
Frank snapped on his light and started back down the tunnel. Joe scrambled to his feet and followed. As they moved back around the bend again, they could feel the movement of air on their cheeks.
"The air current seems to flow from somewhere up above," Frank said, aiming his light toward the roof.
"It does!" Joe exclaimed. "See that crack?"
High overhead, well out of reach, was a rocky shelf protruding from the wall. Frank grabbed a handful of dust and tossed it up to the shelf. Some dropped on the edge, but the rest remained in the air and then slowly drifted away out of sight.
"That's it!" Joe said excitedly. "There's something beyond! It must lead to an exit."
Frank braced himself against the wall. "Up you go, Joe!"
Quickly Joe climbed to his brother's shoulders and found he could easily reach the rocky shelf.
Joe gripped the edge and pulled himself upward. Then he lay on his stomach and, reaching down, grasped Frank's hand in a fireman's grip. A second later Frank was seated beside Joe.
When the Hardys turned, they found still another tunnel facing them. This one slanted upward from the shelf and was too low-roofed for anyone to walk upright. Aiming their lights ahead, the boys crawled on hands and knees through the cramped area.
Presently a glimmer of daylight showed ahead. Joe was about to exclaim in relief when a murmur of voices suddenly reached the boys' ears.
The Hardys knelt motionless and looked at each other. Were members of the gang just outside the tunnel exit waiting for them?
Frank put a finger to his lips. Without a word the boys resumed their crawling-but more slowly and quietly now-toward the mouth of the passage.
Near the opening they halted. A voice which Frank and Joe recognized as that of the thin man they had overheard at the cemetery was saying: "Those kids ought to be showin' any time now, if the cave-in didn't get 'em."
Then another man, deeper-voiced, chuckled. "If it didn't, we'll trap 'em like rats comin' out of a hole!"
CHAPTER X.
Ambush Trail A PANG of fear shot through Frank and Joe as they realized they were trapped in the mine. A clump of brush partly screened the tunnel mouth, but the Hardys' enemies were waiting outside-ready to seize the boys the moment they appeared!
Scarcely daring to breathe, the boys listened as the thin man went on: "I figured it was them Hardys eavesdroppin' at the graveyard last night." He laughed. "Pretty smart o' me givin' out that hint about Brady's Mine, eh?"
"They fell for it, all right," his partner agreed. "And that crowbar business, too, with the phony code. Best part is, it'll look accidental."
The boys heard a deep-throated chuckle. Joe shot a shamefaced glance at his brother. The crowbar must have been painted to attract their attention and then cunningly planted at a weakly shored part of the tunnel!
The thin man continued, "I'll really get a kick out o' payin' off those brats. Big Al was plenty sore at me 'cause that shotgun setup in the copter didn't work out."
" 'Twasn't your fault, Slim."
"Try tellin' that to Al. He was mad over Slip Gun not gettin' the kids last night. Now he blames me for wastin' time this mornin'."
"How come?"
"Aw, that special business he keeps harpin' on -it's all he thinks about. He wanted us to do some searchin' elsewhere today, but the Hardys comin' here changed his plans."
There was silence for a while. Frank and Joe waited tensely, digesting what they had overheard. Then Slim spoke again.
"Wonder how much longer we'll have to wait? I'm gettin' fed up, perchin' here in this cold."
"Maybe the kids can't find their way out," his partner suggested. "If they ain't dead already, that is."
"You sure the tunnel caved in, Jake?"
"Sure. Sounded like an earthquake. I could see the dust comin' out the front end."
"Did you make certain the tunnel was completely blocked?" Slim asked.
"Well, I didn't actually go inside and look. I might've got trapped. Besides, they didn't show up!"
"You chowderhead!" Slim exploded irritably. "If it ain't blocked, the kids may still be able to squirm out.
Go on back and make sure."
"Okay, okay." Jake sounded as if he were getting to his feet.
"Wait! Got another idea. You fetch their horses and bring 'em back here before you check the tunnel,"
Slim added. "That way, there'll be no chance o' the Hardys pullin' a sneak."
After warning Joe to silence, Frank wriggled forward and peered out through the screen of brush. In the distance he could see Jake's stocky figure heading down the snow-covered mountainside on his way to the mine entrance.
Frank was astonished at how far Jake had gone in a few seconds. Since the two men had conversed in low voices, the speakers had sounded as if they were fairly close to the clump of brush. Now Frank realized his mistake.
The opening was on one side of a narrow draw. Slim was evidently perched out of sight, somewhere higher up the mountainside-probably holding a rifle to cover the boys.
The two men must have thought their conversation was inaudible to anyone else, but the steep-sided draw had caused an echo effect, trapping their voices and reflecting the sound back toward the tunnel.
Frank signaled his brother to crawl forward and join him. Stealthily Joe complied. Several minutes later Jake returned, leading the boys' horses. Slim came down the slope to meet him.
"No sign of 'em," the Hardys heard Jake report.
"Check inside the tunnel," Slim told his partner. "If they didn't get buried by the cave-in, we're supposed to take 'em up to Windy Peak."
The thugs exchanged one or two other remarks, but their conversation was carried away by a surge of icy wind sweeping down the draw.
Jake turned and started off again, heading back to the mine entrance. Slim threw a glance toward the clump of brush to make sure their quarry had not yet emerged. Then he took the boys' horses and trudged toward a stunted, leafless tree growing out of the mountainside.
"Let's jump him!" Joe urged.
Frank had noticed that the man wore a long-barreled revolver in a holster slung at his hip. If he had a rifle, he must have left it at the spot where he and Jake had been waiting.
"It's risky, but we'll try," Frank agreed.
The moaning of the wind would help cover the sound of their footsteps in the snow, and Slim's back was turned as he prepared to tether the horses to the tree. Jake was already out of sight behind a shoulder of the hill.