"Mystery!" repeated Joe. "That his name?"

"Yes, because he's the little feller that's goin' to help us solve this mystery."

Once more, the three boys descended the steep path to the floor of the hollow.

Around them the woods preserved their eerie silence. Even the puppy showed no desire to range about.

Suddenly Frank called a halt. "It's the same as yesterday," he said in a low, perplexed voice. "I'm sure we're being followed!"

The three listened, hardly breathing. But there was nothing to be heard or seen. "All right. Let's go!" Frank signaled finally.

Almost before they knew it, the boys had reached the queer, windowless cabin.

Frank stepped forward and rapped sharply on the door.

Immediately it was pulled inward. A tall, broad-shouldered man with heavy brows, a full mustache, and piercing eyes confronted them.

"Colonel Thunder!" Joe blurted.

59 "Colonel?" the man repeated quizzically in a deep, hearty voice. "Take it easy on the rank, there, boy. You couldn't even call me a buck private, seeing as how I was never in the army!"

"You mean," faltered Chet, "you're not Colonel Bill Thunder, the fearless animal trainer?"

The big man gave a booming laugh. "No. Afraid I'm just plain Walter Donner."

Perplexed, Joe stammered, "Well, Colonel Thun-I mean, Mr. Donner-we're afraid that something has happened to a friend of ours, Captain Thomas Maguire-he owns a cabin on the other side of the hollow. He disappeared from his cabin at least two nights ago!"

Immediately Mr. Donner's genial face became serious. "Hmm. Better come in awhile, boys. Just tie the puppy outside there, will you?"

Frank, Joe, and Chet followed their host into a tidy little room furnished with rustic wooden table and chairs. "Leave the door open for the light. Sit down here. I'll be back in a minute."

The tall man ducked easily through a low, narrow doorway into the kitchen beyond. The boys could hear pots being moved about, and a door being closed.

In a moment Donner was back.

"Now," he addressed them, "who is Captain Maguire, and what's happened to him?

Let's get all the details."

The boys introduced themselves, then Joe explained, "He's a friend of ours who lives on the 60 edge of the hollow. The captain was expecting us. When we arrived, day before yesterday, there was no sign of him. He'd vanished. We tracked him into the hollow, where we found his flashlight and two shotgun sh.e.l.ls that he probably fired."

"Yes!" Donner broke in. "There was some shooting the other night. At first I thought it was a hunter. But I didn't hear any dogs, which are used for hunting c.o.o.n, or anything legal. So I a.s.sumed it was somebody poaching deer.

As for your friend, I'm sorry. I never heard of him."

"Well, thanks anyhow, Mr. Donner," said Frank. "But say-would you know anything about the dogs we understand are disappearing in the neighborhood? We promised to look out for a puppy that's missing."

Thoughtfully, the big man frowned. "Very likely a dog thief. You see, there's a big illegal market on dogs for medical experimentation. I'd like to get my hands on the wretch who steals them," he added indignantly. "You see, I like animals!"

"We did see something else suspicious, yesterday," Frank went on. "A strange person spying on us. He looked-well, he seemed half wild."

"There I can help you," declared Mr. Donner, raising his finger. "You must 21 mean Simon. He's a mute boy who lives with his widowed mother over in the next valley. He can hear, but he lost 61 his voice by an injury to his throat, I understand, even before he learned to talk. He runs wild in the hollow all summer. Lives on berries and whatever he can pilfer from nearby farms."

"Is he dangerous?" Chet asked.

"Mmm-I'd keep away from him. He'd just as soon heave a rock at you as not. You know, it might be Simon who is making off with these dogs. Animals and birds seem to interest him."

"Brrr," Chet shuddered. "I don't see how you stand it here, Mr. Donner. Boys running half wild-the witch shrieking at night."

At this their host's eyes twinkled with amus.e.m.e.nt. "Well, young fellow," he said to Chet with a wink, "intelligence tells me it's certainly no witch. But I'll have to admit every time I hear the screams, chills run up and down my spine!"

Frank and Joe, thinking how they had been startled by the owl, grinned also. A soft popping sound was heard from the kitchen.

"There's my coffee," Donner announced abruptly. "Come into the kitchen, boys."

With eager curiosity Frank, Joe, and Chet followed their host through the narrow doorway. They found themselves in a small windowless kitchen lighted by two kerosene lamps. There was a little wood stove for warmth, but Donner cooked on a small gasoline range. In a moment he had whipped up cocoa for them and poured out coffee for himself.

62 "Yes, I camp out here," he said, as the four sat around the plank table near a ventilation flue. "I come for a rest. I take it easy, and raise a few sheep.

It's a quiet place."

"Quiet is right," Chet agreed. "You'd never know it was here!"

"Ah, but that was the idea," said Donner. "The idea of living in the cabin, I mean. I guess you could call me a hermit.

"I love this cabin. You notice the way it blends with the surroundings? Take a look at the back wall of this kitchen. See? Solid rock. That's the rock face of the hollow. This cabin is over a hundred years old. Do you know what was going on then?"

"Let me see," said Joe. "That would be just about the time of the Civil War."

"Right. This was one of the stations on the Underground Railway-the route for smuggling runaway slaves up to Canada. That's why it's so well hidden, and has no windows, no lights to give it away at night. It's small, but comfortable."

While he examined the unusual little house, one fact stuck in Joe's mind: There seemed to be only one door in the place; the one at the front. How was a runaway slave supposed to escape if he were surprised here? Besides, hadn't he heard a door closing earlier, or had he imagined it?

While Joe wondered, suddenly there came an urgent knocking.

CHAPTER VIII.

Rock Barrage the sunlight streaming into the hermit's cabin was suddenly blocked off by the stocky figure of Sheriff Ecker.

" 'Morning, Donner," he said, as the tall man came forward with hand outstretched. "Sorry to break in, but we're going to need your help."

By this time Frank, Joe, and diet had come from the kitchen. "Oh, the boys found you first, did they?" The sheriff spoke in a gruff but friendly voice.

He was dressed for the wilderness in high-top boots and a st.u.r.dy belt from which hung a heavy revolver in its holster. Three men were standing together behind the sheriff.

"Well, here's your search party," Ecker said to Joe. "It's not much of a posse-three men are all I can spare, but we'll do what we can. With you fellows and Mr. Donner here, we'll have eight, and that's pretty good.

Sorry I couldn't get hold of a good dog to take along."

"That's all right, Sheriff," Chet spoke up. "We have Mystery 1"

"Our beagle," Joe explained hastily.

"Search party?" repeated Donner. "That sounds terribly official to me, Sheriff!"

Sheriff Ecker shot a quick look at the smiling Donner. "Did the boys tell you what's up?"

"Well, they did say something about their captain friend being missing. He probably just went for a long hike in the woods. I'd no idea it was so important that the sheriff personally would lead a search party in these out-of-the-way parts," he added, smiling.

Sheriff Ecker frowned, obviously reminded of other urgent matters. Joe and Frank glanced at each other-would the man change his mind about conducting the search? But Ecker merely said: "I'd like you to come along, Mr. Donner, since you know the hollow so well."

"By all means," agreed the big man. "But now that you are here, come in and have a look at my little retreat, Sheriff. It's over a hundred years old. I was just telling the boys that it used to be a hide-out for runaway slaves."

Hospitably, Donner conducted Ecker through the cabin, while the boys waited.

Joe went 65 to introduce himself to the three deputies.

Chet, meanwhile, accompanied by the frisky young puppy, wandered over to the three-cornered sheep pen and peered inside. Frank stayed near the door of Donner's house. He stared thoughtfully at the ground. Something shiny that lay deep in the tall meadow gra.s.s caught his eye. Un.o.bserved by the others, he stooped down, examined the object, and slipped it into his pocket, just before Donner and the sheriff appeared.

"Ready to go, boys?" Donner boomed.

The group now formed under his direction. Donner had put on a dapper felt hat with bright-colored trout flies hooked in the band. With an amused grin he was stuffing a long-barreled target pistol with a fancy pearl handle into his belt.

"Now I feel like a real deputy," he joked. Frank and Chet took their places with Joe.

"Now, my husky young friend," Donner went on, gripping Chet's shoulder, "suppose you come up front with your dog. Black Hollow has two kinds of terrain, woods on the bottom and rock on the sides. We'll take the woods first, and the rocks later."

Quickly the searchers were told by Sheriff Ecker to fan out in order to cover as much ground as possible. Each person was to keep the man to the right of him in plain sight, and was responsible for the area between them.

66 Chet, with Mystery eagerly sniffing and straining at his homemade leash, was placed near the center, slightly in advance of the rest. Sheriff Ecker stationed himself on the left wing, and Frank and Joe had the extreme right.

Donner took the middle, so he could call directions. In this order the party advanced into the thick woods on the hunt for Captain Maguire.

The tangled undergrowth, dim light, and the numerous trees growing densely together made progress difficult and slow.

"Sheriff!" Donner called out. "There's a little gully over near you. Check it.

Maguire may have fallen into it."

In a minute the report came back, "n.o.body there!"

Another time the woodsman sang out jokingly, "You-Joe Hardy-you'll be coming to a hollow tree. Better look and see if your friend's inside!"

Joe smiled faintly, but he was beginning to be annoyed at Donner's rather lighthearted approach to the affair. "Treats the whole thing like a lark," the young sleuth thought.

All the while his keen eyes scanned the ground, bushes, and heavy undergrowth.

23 Frank and Chet also were constantly on the alert.

The search continued through the gloomy hollow. All at once, Mystery gave a high-pitched yap at something that had startled him.

"A man!" Chet shouted. "I see a body!"

67 From both sides the searchers came pounding toward him. All stared ahead into the dark woods. Ahead lay the huddled figure of a man in black coat and cap, and gray trousers!

Tensely, with Mystery bounding along, they pressed forward. Frank and Joe were the first to reach the figure. Both gasped in relief.

"It's only a fallen tree limb!" Joe exclaimed, as the others came up.

"Some eyes you've got, Morton," Donner roared. The deputies shook their heads in a half-amused, half-exasperated gesture.

"Well, it looked like a body-from far away," Chet apologized ruefully.

"Might as well call a halt and rest now that we're all together," Sheriff Ecker interposed.

Eager to make amends, Chet opened his knapsack and pa.s.sed around tuna-fish, egg-salad, and ham-and-cheese sandwiches. The three deputies sat down on the tree limb that had fooled Chet. Frank, Joe, and the sheriff squatted on their heels while Donner lounged against a tree.

"It's noon, but you'd never know it in these dark woods," Sheriff Ecker commented.

While Chet went from man to man with a big Thermos of coffee, Frank brought a tiny transistor radio from his pocket and turned on the twelve-o'clock news.

The swift, precise voice of an announcer roused the search party's attention: 68 "New Jersey and Pennsylvania State Police were forced to admit defeat this morning in their attempt to recover thousands of dollars' worth of surgical equipment stolen last night from a truck en route to New Jersey.

"Daring hijackers stopped the tractor trailer carrying the equipment, knocked the driver unconscious, and apparently fled in a vehicle of their own. No trace of them has been discovered."

Frank and Joe exchanged meaningful glances. This news indicated their father's work on the case was far from finished!

"Officials emphasized," the broadcaster continued, "that this robbery was only the latest in a series of many which have taken place in the area recently.

Combined efforts of law-enforcement agencies in both states to round up the hijackers have so far ended in total failure."

"Turn it off," the sheriff snapped.

Donner, however, merely chuckled and shook his head with amus.e.m.e.nt. "Now isn't that just like our State Police!" he said. "Just don't want to work overtime, probably. No wonder they can't keep up with these hijackers. When thieves are on a job they don't worry about the hours!

"Now, Sheriff, you tell me," the big man went on, "why aren't these criminals caught? All it would take, it seems to me, is a system of alerting all policemen within a reasonable radius, and posting them on all possible escape routes."

69 "Mr. Donner, I know you mean well," answered Ecker, frowning, "but you're hittin' kind of close to home. I was out all night myself, and my men too. We were out the night before that. I'd be watching the roads right now, if I wasn't here searching for this man who's disappeared. A policeman can't do two things at once, y'know -no more than another man."

"You're right, Sheriff, and I'm sorry," Walter Donner apologized. "Let's finish this search."

Accordingly, the party spread out in line again, and the hunt went on. By midafternoon the searchers had thoroughly combed the wooded valley floor without discovering a clue to Captain Maguire's whereabouts. Now they found themselves up against the steep, rocky side of the hollow.