There were certainly some marks in the dust, but not many, for somebody's feet had evidently scuffled about just there. Fatty sat himself down in exactly the same place in which the old man had been. He stared hard at the dust.

So did the others. "That looks like a letter W," said Fatty, at last, pointing. "Then there's a letter half rubbed out. And then that looks like an X. Then all the rest of the letters have been brushed out where people have walked on them. Blow!"

"W—something—X," said Larry, who was good at crosswords, with their missing letters. "W—A—X it might be that."

And then exactly the same thought struck all the Find-Outers at the same moment.

"WAXworks! That's what the word was!"

They stared at one another in the greatest excitement. Waxworks! Were the pearls hidden somewhere in the Waxworks Hall? It was a very likely place, a place that all the gang knew well. And Number Three had kept looking in at the door that afternoon.

"He kept peeping in—but he couldn't go and get the pearls, because there were too many people there!" said Fatty. "Golly, we've got the idea now! Now we've only got to go there and hunt, and we'll find the pearls somewhere—in the cupboard, perhaps, or under a floorboard."

"Let's go and look for them straightaway," said Larry, getting up. "Come on."

"We can't very well, under the nose of that red-haired boy," said Fatty. "Still, we'll go down to the Hall anyway." They set off and soon came to the Fair again.

"There's the red-headed boy over there—he's gone to his tea or something," said Bets, pointing. "Has he left the Hall empty for once?"

They hurried to see. There was a badly written notice stuck on the locked door. "Gone for tea. Back soon."

"Aha!" said Fatty, his eyes gleaming. "This couldn't be better for us. We'll get in at that window, Larry. It's sure to be open still."

It was still unfastened, and the children climbed in excitedly, almost tumbling on to the floor in their eagerness to go hunting for the pearls.

"Behind the curtains, in the cupboards, up the chimney, every place you can think of!" said Fatty, in a thrilled voice. "Go to it, Find-Outers. Solve the mystery if you can!"

Then such a hunt began. Every cupboard, every shelf, every nook and cranny in that Hall were searched by the bright-eyed Find-Outers. Buster, eager to help, though without the faintest idea of what they were looking for, scrabbled about too, having a vague hope that it might be rabbits.

Fatty even examined the floor-boards, but none of them was loose. At last, when it seemed as if every single place had been searched, the five children sat down to rest and discuss the matter.

"I suppose it is here, that necklace!" said Daisy. "I'm beginning to think it isn't."

"I feel as if I'm playing Hunt-the-Thimble," said Bets. "Where is the thimble? It must be in some jolly good place, that necklace!”

Fatty stared at Bets. "Bets," he said, "supposing we went out of the room, and you had to hide a pearl necklace somewhere here, what difficult place would you think of?"

Bets looked round the Hall and considered. "Well, Fatty," she said, "I've always noticed that when people play Hunt-the-Thimble, the most difficult hiding-places to find are the easiest ones really."

"What do you mean? " demanded Pip.

"Well," said Bets, "I remember looking everywhere for the thimble once—and nobody found it—and yet where do you think it was? On Mother's finger!"

Fatty was listening hard to Bets. "Go on, Bets," he said. "Suppose you had to hide that pearl necklace here, in this Hall—where would you hide it? It would have to be a good place, easy to get at—and yet one where ordinary people would never dream of looking for a valuable necklace."

Bets considered again. Then she gave a little smile. "Well, I know where I'd put it!" she said. "Of course I'd know! And it would be under the noses of every one, and yet nobody would notice it!"

"Where? " cried every one.

"I'll tell you," said Bets. "See Queen Elizabeth over there, in her grand clothes and jewels, standing looking so proud and haughty? Well, I'd put the pearl necklace round her neck with all the other necklaces, of course—and nobody would ever guess that among the false Woolworth ones there was a REAL one!"

Fatty leapt to his feet. "Bets, you're right. I'd got that idea half in my own mind, and now you've said all that, I'm sure you're right! I bet the necklace is there! Clever old Bets!"

They all ran to the stately wax figure of Queen Elizabeth whose neck was hung with brilliant necklaces of all kinds. Among them was a double necklace of beautifully graded pearls, with a diamond clasp—at least, the children felt sure it was a diamond one. Fatty lifted the necklace carefully off the figure's neck, undoing the clasp first.

The pearls shone softly. It was clear even to the children's eyes that they were not cheap ones, bought at a store. They were lovely, really lovely.

"These must be the missing pearls!" said Fatty, exultantly. "They really must! Golly, we've found them. We've solved that mystery! What will the Inspector say? Let's go and ring him up."

They climbed out of the window and hurried to their bicycles. Fatty had the wonderful necklace safely in his pocket. He couldn't believe that they really had found it—and in such an easy place too!

"But a jolly clever one," said Fatty. "To think it was under the eyes of scores of people today—and nobody guessed! It was safer on Queen Elizabeth's neck than anywhere else!"

"Look out—there's Goon!" said Larry.

"And Inspector Jenks with him!” cried Bets in delight. "Shall we tell him?"

"Leave it to me," ordered Fatty. "Good evening, Inspector. Come to hunt for the necklace too?"

"Frederick," said the Inspector. "I believe you were bicycling after the member of the gang called Number Three this afternoon, weren't you?"

"Yes, sir," said Fatty. "With Mr. Goon, as well, sir."

"Well, unfortunately he gave Mr. Goon the slip," said the Inspector. "Mr. Goon rang me up, and I came over because it is imperative that we keep an eye on Number Three, if we can, owing to his knowledge of where the pearls are hidden. Did you by any chance see the man, after you had got your puncture?"

"No, sir," said Fatty. "Haven't set eyes on him."

The Inspector gave an annoyed exclamation. "We must get Number Three. We've found out that he is the ring-leader, and the man we want most of all! And now if he get those pearls, wherever they are, and clears off, sooner or later these burglaries will start all over again. He will find it quite easy to start a new gang."

Mr. Goon looked very down in the mouth. He also looked hot and tired.

"He's a clever fellow, sir," he said to the Inspector. "Very clever. I don't know how he managed to give me the slip, sir."

"Never mind, Mr. Goon," said Fatty comfortingly. "I can tell the Inspector where the pearls are, and how you can catch Number Three if you want to."

Mr. Goon stared disbelievingly at Fatty. "Gah!" he said. "You make me tired. Talking a lot of tommy-rot! I don't believe a word of it!"

"What do you mean, Frederick?" said the Inspector, startled.

Fatty drew the pearl necklace out of his pocket. Mr. Goon gasped and his eyes bulged more than ever. The Inspector stared in amazement too. He took the pearls from Fatty. All the children crowded round in excitement.

"Frederick! These are the missing pearls! A double row of the very finest graded pearls there are," said the Inspector. "My dear boy—where did you get them!"

"Oh—we played a little game of Hunt-the-Thimble with Bets—and she told us where they were," said Fatty, and Mr. Goon gave a disbelieving snort. "They were round Queen Elizabeth's neck, in the Waxworks Hall, Inspector—a very clever place—and Bets thought of it!"

"Certainly a very clever place," said the Inspector, "and a very clever thought of yours, little Bets, if I may say so!" he said, turning to the delighted little girl. "They must have been shining there under the noses of hundreds of people today—and nobody so much as guessed! But now, Frederick—how do you propose that we lay hands on Number Three?”

"Well, sir—he knows that the pearls were hidden in the Waxworks Hall," said Fatty, "and maybe knows too that they were on Queen Elizabeth's neck—so he's bound to go back for them, sir, when every one has gone, and the Hall is dark and empty. Oh, sir—could I come and hide in the Hall tonight when you do your spot of arresting!"

"No," said the Inspector. "I'm afraid not. I'll have three men posted there. See to that straight-away, please, Goon. Er—I'm sure we can congratulate the Find-Outers on solving our problems for us in such a praiseworthy way—don't you think so, Goon? "

Goon murmured something that sounded suspiciously like "Gah!"

"What did you say, Goon?" said the Inspector. "You were agreeing with me, I imagine?"

"Er—yessir, yessir," said Goon hurriedly, and turned a familiar purple. "I'll get the men now, sir."

He hurried off, and the children saw that even the back of poor Goon's neck was bright purple too. The Inspector slipped the pearls into his pocket and beamed all round.

"Well, once more, you've done remarkably well," he said, "though I must confess I was a little annoyed with you, Frederick, for running heedlessly into danger. Still, as usual, you've used your brains, and have helped a great deal. Especially little Bets, if she really did think where the necklace might be."

"Oh, she did," said every one, even Pip, and Bets went as red as a tomato with pride. She might be the youngest of the Find-Outers—but she was just as good as any of them!

"Now—I can take it that you will respect my wishes and not go near the Waxworks Hail tonight?" said the Inspector, raising his eyebrows at them all. They nodded vigorously.

"You can trust us, Inspector. But tell us in the morning if you've got Number Three, won't you?" said Fatty.

And in the morning the Find-Outers heard what had happened. Number Three had let himself into the Hall at midnight. He had walked to Queen Elizabeth, and had fumbled at the jewellery round her neck—and just as he was fumbling, out stepped three burly men and caught him!

"Now he's in a cell thinking sadly over his sins," said the Inspector, over (the telephone. "We've got the whole gang—and the necklace too. Good work! We certainly couldn't have done without you Find-Outers. What about you all joining my police-force? We could do with you!"

"Oh, how I wish we could!" said Bets, afterwards. "I suppose he didn't really mean it, did he? "

"And now to think we've got to help with our packing and go back to school!” said Pip, in disgust. "After ail our fine detective work, we've got to go and learn the chief rivers of the world, and the date when Queen Elizabeth came to the throne, and how much wheat Canada grows, and..."

"Never mind—well have another Mystery to solve next hols," said Bets happily. "Won't we, Fatty?"

Fatty grinned at her. "I hope so, little Bets," he said. "I really do hope so!"

I hope so too. It would be most disappointing if they didn't!