Buster stood by the gate, near Fatty, looking up into his master’s face as if he understood every word.

“There!” said Fatty, pleased. “He’ll stay on guard all the morning if we want him to.”

But as soon as they went down the drive again, Buster scampered after them! He didn’t want to stand at the front gate if they were all going to leave him!

“He’s not so clever as we thought,” said Pip. “You’ll never get him to stay there, Fatty!”

“Yes, I shall,” said Fatty, and took Buster firmly back to the gate. He took off his overcoat and removed his pullover. He put it down just inside the gate, at the edge of the drive.

“Guard it, Buster, guard it!” said Fatty commandingly. “Sit on it - that’s right. It’s my best pullover. Guard it for me, old fellow!”

Buster knew perfectly well how to guard things, and once he sat on them, would stay with them till Fatty came back and called him off. Now he made no attempt to leave the pullover and follow the others; he sat there as good as gold, looking mournfully after them.

“Poor Buster! He does want to come. I bet he knows you’ve played a trick on him, Fatty,” said Pip. “His ears are down and his tail hasn’t got a wag left in it.”

“Well, anyway he’ll give us warning if any one comes,” said Fatty. “Not that I’m expecting any one. But you never know. Detectives have to be prepared for anything.”

“It nice to be Find-Outers again,” said Bets happily. “Oh, Pip! - is this the tree you climbed?”

It was. It was such an easy one to climb that even Bets, with Fatty’s help, could climb from branch to branch, and reach the place from which she could peer into the secret room.

It was just as Pip and seen it the day before - fully furnished, comfortable looking, and very dusty. The children all took their turn at staring in. It had been exciting to hear of it, but it was even more thrilling really to see it. Whatever was the room used for?

“Well, I’m going off to the house-agent’s,” said Fatty, shinning down the tree. “You take charge now, Larry, and snoop around the house. Look out for footprints, bits of torn paper, cigarette-ends - anything that might be clues.”

“Ooh!” said Bets joyfully. “I do love looking for clues.”

“You called them glues last year,” said Pip. “Do you remember?”

Bets didn’t want to remember things like that, so she didn’t answer. They all climbed down the tree and began to look around the house.

“Everywhere is empty,” said Larry. “I wish we could find a window left open or something. Then we could get inside.”

But not a window was left open, not even a crack. Not only that, but it seemed as if every window had a double fastening.

“Whoever lived here before must have been afraid of burglars,” said Daisy. “Short of smashing a window or breaking down a door, I don’t see how any one could possibly get into this house.”

They looked for footprints, but found none. Neither was there a cigarette-end, or even a scrap of paper to be seen.

“Not a single clue!” said Bets sorrowfully.

“Look at all our footprints!” said Daisy, pointing to where they showed in the muddy ground. “Plenty of clues left by our feet to show we’ve been here! I think we ought to have been more careful.”

“Well, we can’t do anything about it now,” said Pip. “Listen - is that Buster barking?”

It was. He was barking madly, and the four children listened uneasily. Fatty had gone to the village. He wasn’t there, with his quick cleverness to take charge. Pip, Daisy, and Bets looked at Larry.

“What shall we do?” said Bets. “I can hear some one coming down the drive!”

“Hide!” said Larry. “Quick, scatter behind bushes!”

They scattered, and Bets with a beating heart hid behind rather a small bush, hoping she would not be seen.

To her horror it was the familiar dark-blue uniform worn by the village policeman that she saw coming round the corner of the house! He was wheeling his bicycle.

It was a real piece of bad luck that he had passed that way this morning, for he rarely cycled down the lane that led to Milton House. But he had to go to an outlying farm to speak to a farmer about straying cows, and, as the usual field path was under water, Mr. Goon had taken a longer way round, which took him by Milton House.

He was thinking of a nice hot dinner when he cycled slowly by. He hadn’t even seen Buster sitting patiently on Fatty’s pullover; but Buster not only saw him and heard him, but smelt him too - and it was not a smell that Buster liked.

Mr. Goon was his enemy. In fact, Mr. Goon was the natural enemy of all little dogs, though big ones he tried to make friends with. Buster couldn’t help barking defiantly when he saw Mr. Goon sailing ponderously by on his bicycle. He made the policeman jump. Mr. Goon locked to see where the barking came from, and to his enormous surprise saw Buster, sitting down on a heap of wool, barking furiously.

“Ho!” said Mr. Goon, getting off his bike at once. “You the dog belonging to that fat boy? If you’re here, he’s here - and up to some mischief, I don’t doubt!”

He walked in at the gate. Buster barked more loudly than ever, but he didn’t get up off Fatty’s pullover. No, he had been trusted to guard that, and he would guard it with his life, if need be!

Mr. Goon was pleased to find that Buster didn’t hover round his ankles as he usually did, but he was very curious to know what Buster was sitting on. He bent down and gave the pullover a jerk.

Buster was so furious that he almost snapped one of Mr. Goon’s fingers off. The policeman hurriedly took his hand away.

“Spiteful creature! Vicious dog! You ought to be destroyed, you ought,” said Mr. Goon severely. “What you want is a good thrashing, and wouldn’t I like to give it to you?”

Buster said some rude things to Mr. Goon in a perfect torrent of barks. The policeman walked by him, keeping his bicycle between himself and Buster, and went up the drive. He felt certain he would soon see Fatty.

He came round the side of the house into the big garden at the back. He saw no one. But he did see all the many footprints in the mud. He leaned his bike against the house and began to examine them with interest.

Then he suddenly caught sight of the top of Bets’ red beret behind her bush. He straightened himself up and shouted:

“Hie, you! I can see you! You come on out from behind that bush!”

Poor Bets came out, trembling. Mr. Goon looked her up and down.

“Ah! One of them Hilton kids again. Can’t keep out of mischief, can you? Where are the others? Where’s that fat boy - and have you got that Frenchy fellow with you? I want to talk to him, I do!”

As soon as poor trembling Bets showed herself, the others came out too. They couldn’t let little Bets bear the brunt of Clear-Orf’s scolding. The policeman was surprised to see so many children coming out from behind the bushes.

“Now what are you doing? Playing hide-and-seek on somebody’s private property?” he said. “I suppose you think because you’re friendly with Inspector Jenks you can do anything you like. But let me tell you, you can’t. I’m in charge of this here village, see? And any nonsense I shall report straight to your parents!”

“Oh, Mr. Goon, is it wrong to play hide-and-seek in the grounds of an empty house?” said Larry, in an innocent voice. “We’re so sorry. Nobody ever told us that before.”

Mr. Goon did one of his snorts. “You’re up to some mischief, I’ll be bound,” he said. “What are you here for? You’d better tell me, see? If there’s anything going on, I’ve got to know about it sooner of later.”

Larry knew that Clear-Orf suspected them of being there because of some new mystery, and he was annoyed to think the policeman had stumbled upon the very place where the mystery was. He decided the best thing to do was to go at once, and make Mr. Goon think they had only been playing hide-and-seek, as he had so obligingly suggested to them.