He halted suddenly, his arm extended and trembling. A loud eerie moan floated through the tunnel.

“Aaaaaahhhh… oooooohh… oooo!”

“Oh, no! Not again!” Shelby cried. Quickly, he reached into his pocket and produced the slender object he had used before. He put it to his lips. Again it made no sound.

The huge walls rustled and closed.

Jupiter, listening intently, smiled. He flicked on his torch.

Caught in his glaring beam, they saw huge, leaping shapes coming at them, their eyes glowing, their jaws open, sharp teeth menacing.

“Look out!” Pete yelled. “Those furry animals — ”

Then he gasped and grinned sheepishly. “I mean, dogs,” he added. “Wow! What a dope!”

Arthur Shelby groaned too. “Too late,” he sighed.

The first animal bounded up to them, barking happily. Its long, brushlike tail swept back and forth in a feverish arc. Its dull reddish coat gleamed.

“Red Rover!” Jupe exclaimed. “He’s come back.”

The big setter ignored Jupe’s outstretched arm and leaped for Shelby. The red-headed man backed off, holding his gun outstretched.

“Go away, Rover,” he snapped. “I’m warning you — for the last time — go home!”

The big dog shook its head and whirled round the man. The other dogs came at him, too, backing him up to the wall.

They leaped happily at the man, growling and barking, their tails wagging. Once more, Shelby waved at them with his gun. His face was pale, shining with sweat.

“It’s no use, Mr. Shelby,” Jupe said. “You can’t shoot them. You like dogs too much. And they’re certainly crazy about you.”

The thin, red-headed man regarded the leaping animals and lowered his gun.

“Yeah,” he said morosely. “Crazy about me. That’s it, all right.”

He looked blankly at the slender metal object in his hand, then shrugged and put it back in his pocket. He put his hand down and almost, unconsciously stroked the heads of the happy dogs.

“Now what?” he asked, speaking to himself.

“I’ve an idea, sir, if you care to listen,” Jupe said.

“You have?” The pale eyes stared at the stocky boy.

Jupiter Jones nodded. “Yes, sir. It’s based largely on the idea that you’re really a practical joker, not a greedy criminal. Would you care to hear it?”

The red-haired man nodded curtly.

“Put everything back. We’ll help you, if you like,” Jupe said. “You might want to leave the hole you drilled in the wall, just as it is. It will be your joke on them. That you had the chance to take all that gold, and you didn’t. We won’t tell, and they’ll never know who did it — or rather who nearly did it!”

When Pete, Bob and Jupiter entered Alfred Hitchcock’s office two days later, the famous director was seated at his desk, reading a newspaper. He motioned them to his big, comfortable chairs.

“Sit down, boys,” he said. “I’ll be with you as soon as I finish this interesting article in the papers.”

They sat and waited patiently. Finally, the director folded the paper and put it aside on his desk.

“So!” he boomed in his hearty voice. “I suggest a case for you concerning the missing dog of an old friend. And what happens? Not only his, but several others are returned. I also see a column in the Seaside newspaper telling of some bizarre plot to rob a large bank. The heading reads: ‘BANK OFFICIALS PUZZLED BY CONTRITE AND CONTRARY CROOKS!’ Was this all your doing? I must admit I am puzzled, too.”

Jupe cleared his throat. “Yes, sir. It was. They were — I mean, sir — yes, we’re kind of responsible for everything.”

Mr. Hitchcock held up his hand. “Your modesty, lad, is most laudable. Still, I would rather hold my own praise in abeyance until I completely understand how you three solved this unique mystery of the missing dogs.”

“Well, sir,” Jupe said. “Actually you helped us a great deal in solving the mystery, sir, when you showed us that old film Mr. Allen made with the dragon.”

“Ah, yes,” Mr. Hitchcock said. “And, as I recall, there was some talk about you boys actually encountering one of those rather fantastic beasts.”

“We sure did,” Pete said abruptly. “And we’re lucky to be alive to tell about it. Even if it wasn’t real.”

“Incredible!” Mr. Hitchcock murmured. “The very real menace of a dragon that wasn’t real. I should like very much to hear about it.”

Bob Andrews whipped out his note book. He proceeded to tell how the investigation had run into a snag at the very beginning, and then how they had managed to pick up the threads that ultimately led to the solution of their original mystery. Mr. Hitchcock listened attentively.

“Your Mr. Shelby sounds like a most ingenious and interesting man,” he said. “Do I understand you correctly when you say he voluntarily gave up his foolproof plan to steal several million dollars’ worth of gold, rather than hurt you and some dogs?”

“Yes, sir,” Jupiter said. “He kept the dogs alive and fed them. He had to tranquillize them to keep them quiet and out of his way. He told us he was going to turn them all loose when he left the cave for the last time with the dragon and the gold.

“He could have forced us at gunpoint to help him carry out the gold after the Morgan brothers ran away. He could have taken enough to be wealthy. He didn’t need the entire ten million dollars.”

Mr. Hitchcock drummed his fingers on the desk. “And his original plan was actually to run the dragon underwater at night, in conjunction with those villainous Morgans?”

Jupe nodded. “I thought the dragon was too light, but he had calculated his ballast in advance — the heavy gold bars. He had to test his dragon in the water, at first, by loading it with rocks. As a matter of fact, that’s how your friend Mr. Allen happened to see the dragon. It was out on a test run, while he was looking for Red Rover.”

“And your clue to Shelby’s part in it was his cold?”

Jupe smiled weakly. “He had a bad cough when we met him. So I associated him with the coughing of the dragon. Later I found out it coughed when it stalled. That was partly due to wet wiring, from the many experiments in the sea.”

“But your mysterious phone call — the ghostly, rasping voice — that was really Shelby?”

Jupe nodded.

Mr. Hitchcock shook his head. “This Arthur Shelby doesn’t sound like a typical crook at all. How did he happen to tie up with such low characters as the Morgan boys?”

“They had a salvage rig and he knew them as tough men who would do anything. He needed their help for the work in the cave, drilling into the bank vault through the concrete wall of the tunnel, and then getting the gold out. When he offered them a million dollars, they were more than willing.”

“And how did they propose to get the gold from the sub into the boat?”

“After he got under way, the Morgans with their underwater gear were to attach a cable from the sub to their tug, and tow it out to sea. When they were far enough out, they were going to surface the sub and unload the gold bars. Then they were going to head for Mexico.”

Mr. Hitchcock nodded. “Why a dragon, at all?”

“That was from knowing your friend Mr. Allen and his film background, using dragons to scare people. You see, at first Shelby just thought it would be a new way to play a practical joke on his neighbour. But when he heard of a large shipment of gold bars to that bank, he decided to carry out a robbery. He figured the dragon could easily be converted into a functioning sub. It suited his kind of offbeat thinking — a funny and perfect way to get the gold from the bank through the old tunnel to the sea. It backfired on him because it was the oddity of the dragon that kept us interested in trying to solve the mystery.”

“I should have imagined Mr. Shelby to be without sufficient funds to construct something as elaborate as that dragon,” Mr. Hitchcock said.