The moon rode high in the heavens as the cabin cruiser let go its anchor in a cove off the Kippenberg estate. Penny who had been dozing for the past hour in her self-imposed prison started up in alarm as Jerry nudged her in the ribs.

“Wake up,” he whispered. “We’re here.”

“At the estate?”

“I think so.”

On the deck above their heads they could hear the men talking together.

“You’ll come along with us, Atherwald,” Aaron Dietz said. “Flora, you stay here and guard the boat. If you see anyone watching or acting suspiciously, blow the whistle two short blasts.”

“I don’t want to stay here alone,” the girl whimpered. “I’m afraid.”

“You’ll do as I say,” the man ordered harshly. “Get started, Gus. It’s two o’clock now. We won’t have many hours before daylight.”
[193]

In making her plans Penny had not once considered that the men might leave a guard on the cruiser. With the girl posted as a lookout they were still prisoners in the cabin.

“We have to get out of here now or never,” she whispered. “What shall we do about Flora?”

“We’ll rush her and take a chance on the whistle.”

They slipped out of their hiding place and crawled noiselessly up the steep stairway. Pausing there, they watched the shadowy figure of the girl in the bow of the boat. She was quite alone, for her companions had disappeared into the woods.

“Now!” commanded Jerry in a whisper.

With a quick rush he and Penny were across the deck. They approached Flora from behind and were upon her before she could turn her head. Jerry grasped her arms while Penny clapped a hand over her mouth to prevent a scream. Although the girl fought fiercely, she was no match for two persons.

Stripping off her sash, Penny gave it to Jerry to use as a gag. They bound the girl’s wrists and ankles, then carried her down into the cabin.

“I hate to leave her like that,” said Penny as they went back on deck.

“Don’t waste your sympathy,” replied Jerry. “She doesn’t deserve it. Anyway, we’ll soon set her free. We must bring the police now.”

“The nearest house with a telephone is about a half mile away.”
[194]

“It won’t take us long to cover the distance,” Jerry said, helping her down from the boat.

“You go alone,” urged Penny. “I’ll stay here and keep watch.”

“I don’t like to leave you.”

“Go on.” Penny gave him a little push. “And hurry!”

After Jerry had reluctantly left, she plunged into the trees, carefully picking her way along the path which led to the lily pool. A short distance brought her to the clearing. Halting, she saw the three men and Grant Atherwald silhouetted in the bright moonlight. The latter was still handcuffed, guarded by Aaron Dietz who allowed his companions to do the hard labor.

Gus and Jake had broken open the door of the stone tower. The soft purr of a motor told Penny that they had started draining the pool. She wondered what the men would do when they discovered that the tank contained a very live alligator.

“It ought to put a crimp in their work,” she chuckled. “Mr. Kippenberg couldn’t have chosen a more effective guard for his gold.”

But gradually as the pool drained lower and lower, it struck Penny as odd that the men did not notice the alligator. Belatedly, it occurred to her that the Kippenberg gardener had probably succeeded in getting rid of the monster since her visit to the garden earlier in the day.
[195]

“Something like that would happen,” she thought. “Oh, well, even so Jerry ought to get here with the police in ample time.”

Only the waning of the moon gave indication of how swiftly the night was passing. Penny became alarmed as she observed how fast the pool emptied. Jerry would not have as long as she had anticipated. But surely, he would bring help before it was too late.

Presently, one of the men shut off the motor in the stone tower, saying with quiet jubilance:

“There, she’s empty!”

He jumped down into the tank, and almost at once uttered a cry of discovery.

“Here it is, just as he said! The ring to the trap! Give us some help, Gus.”

With Aaron Dietz and the bewildered bridegroom watching from above, the two men raised the heavy block of cement. Penny drew closer for she did not wish to miss anything. She stood in the shadow of a tree scarcely fifteen yards from where the men worked.

“A stairway leads down into an underground vault!” Jake cried exultantly. “We’ve found the hiding place of the gold.”
[196]

“Toss me your flashlight, Aaron,” called Gus. “We’ll soon have all of the treasure out of here.”

The next ten minutes brought a confused whirl of impressions. Penny’s thoughts were in turmoil. Why didn’t Jerry come with the police? As soon as the men carried the burden of gold to the boat they would discover Flora, bound and gagged. Then they would suspect that a trap had been laid. Oh, why didn’t Jerry hurry?

Gus and Jake had descended into the underground vault. As the light reappeared, Penny was dumbfounded to see that the men were empty handed.

“Nothing down there,” Gus reported in disgust. “Nothing!”

“Then we’ve been tricked!” Aaron Dietz turned furiously upon his prisoner. “You’ll pay for this!”

“I thought the gold was here,” answered Grant Atherwald.

“Lock him up in the vault and start the water running,” advised Jake harshly. “It’s a good way to be rid of him.”

The suggestion appealed to Aaron Dietz. At a nod from him, Atherwald was seized and dragged down into the pool. He was shoved into the vault, but before the two men could lower the heavy cement block into place, a signal from Dietz arrested their action.

“Wait!”
[197]

In her anxiety over Grant Atherwald, Penny had moved closer to the pool. Without realizing that she was exposing herself, she stood so that her shadow fell clearly across the open space. Before she comprehended her danger, Dietz hurled himself upon her, seizing her roughly by the arms.

Penny struggled to free herself but could not. The man’s grip was like steel.

“So you were spying!” he exclaimed harshly.

“I—I was just watching,” Penny stammered. “Don’t you remember me? I am the girl who pulled you out of the river when your car went over the drawbridge.”

The man looked closely at her, and for an instant she dared hope that he would recall her with gratitude. But his face hardened again and he said unfeelingly:

“You know entirely too much, my little girl. This is one story you will never write for your father’s paper. Your curiosity has proven your undoing. You share the fate of............