Penny hooked the cameo pin in the curve of the stick and began raising it inch by inch up the side of the pool.

"If I can get it up high enough reach down and s.n.a.t.c.h it," Penny advised her chum. "Oh, shoot, there it goes!"

The pin had slipped away from the stick and settled once more on the bottom of the pool.

"You can't get it, Penny," Louise insisted. "You're making the alligator all excited by prodding around."

"I don't care about _him_. I'll try once more if I can locate the pin. It seems to be hiding from me now."

The water was so disturbed that Penny could not see the pin or the bottom of the pool. She waited several minutes for the dirt to settle and then gazed down once more.

"There it is!" she exclaimed. "It moved over quite a ways to the right."

Louise flattened herself beside Penny. "Oh, let the pin go," she said.

"No, I think I can get it. Say, there seems to be something else on the bottom of the pool."

"Where?"

Penny pointed, and then, as her chum still could not distinguish anything, parted the lily pads with her stick.

"Yes, I do see something now," Louise declared. "What can it be?"

"Doesn't it look like a metal ring?" Penny asked. She had lost all interest in the cameo pin.

"Yes, it does. Someone probably threw it into the pool."

"But it looks to me as if it's attached to the bottom of the tank, embedded in the cement," Penny said. She bent closer to the water, trying to see.

"Be careful," Louise warned nervously. "That alligator might come up and snap off your nose."

Penny paid no heed.

"It is attached!" she announced in an excited voice. "Louise, do you know what I think?"

"What?"

"It's the ring of a trapdoor!"

"A trapdoor!" Louise echoed incredulously.

"You can see for yourself that it's an iron ring."

"It does look a little like one from here," Louise admitted. "But whoever heard of a trapdoor in a lily pool? No one but you would even think of such a thing. It doesn't make sense."

"Does anything on this estate make sense?"

"The ring might have something to do with draining the pool," Louise said without replying to her chum's question. "I suppose a section of the pool could be lifted up and removed. But I'd never call it a trapdoor."

"I wish we could tell for sure what it is." Penny tried to prod the ring with her stick but it was well beyond her reach. "Maybe the alligator has a room down under the pool where he spends his winters!"

"You're simply filled with ideas today," Louise declared. "What about my pin? Shall we let it go?"

Reminded of her original task, Penny set to work once more, trying to draw the cameo to the edge of the tank. She was so deeply engrossed, that she jumped as her chum touched her on the arm.

"Listen, Penny, I think someone is coming!"

From the path at the right they could hear approaching footsteps and the low murmur of voices.

Penny struggled to her feet, dropping the stick.

"We mustn't be caught here," she whispered.

Taking Louise's hand, she drew the girl into the dense bushes directly behind the pool. Scarcely had they secreted themselves when Sylvia Kippenberg and the head gardener came into view. They seated themselves on a rustic bench not far from where the two girls stood.

"I had to talk with you," Sylvia said to the old man. "The police came this morning and asked so many questions. Mother put them off but they'll be back again."

"They didn't learn about the alligator?" the gardener asked gruffly.

"No, they came here but only stayed a few minutes. I don't think they noticed anything wrong."

"Then that's all right."

"Their investigation is only beginning," Sylvia said nervously. "Mother and I both believe it would be wise to get rid of the alligator."

"Wise but not easy," the gardener replied.

"You'll see what you can do about it?"

"Yes. I'll try to get rid of him."

"Then I guess that's all," Sylvia said, but she made no move to leave.

She sat staring moodily at the pool.

"Anything else on your mind?" asked the gardener.

"I--I wanted to ask you something, but I scarcely know how."

The gardener waited, watching the girl's face intently.

"You never liked Grant Atherwald," she began nervously.

"Say, what are you driving at?" the man asked quickly. "You're not trying to hint that I had anything to do with Grant Atherwald's disappearance?"

The two faced each other and Sylvia's gaze was the first to fall.

"No, no, of course not," she said.

"I don't know any more about his disappearance than you do," the man told her angrily. "I didn't even see him on the day of the wedding."