They walked over the hill, and made their way down the rather secluded lane to Milton House. It was the last house, and stood well back in its own overgrown grounds. It was plain that no gardener had worked there for years. It looked a lonely and desolate place. The house itself was large, high, and rambling, and had two or three absurd little towers.

“Well, there it is - our Mystery House,” said Pip, as they stood and looked at it from the drive. “Now wouldn’t you say that house was completely empty and unlived in? And yet there’s a furnished room at the top of it, where some one must come and live at times!”

The children felt a little shiver go down their backs. It was exciting. Probably no one but themselves and the one who furnished the room knew about that secret.

“Well - let’s take down the house-agent’s name and address,” said Fatty. “Any one seen the board?”

Nobody had. And what was more, there didn’t appear to be one to see. Other empty houses they had passed on their way all had at least one, if not two boards up, with the notice “For Sale. Apply to -” on them. But Milton House didn’t seem to have a board at all.

“But surely it’s for sale?” said Larry, puzzled, when they had made quite certain that there was no For Sale board. “Surely all empty houses are for sale or to be let? The owner wouldn’t want them to stand empty, gradually falling into ruin.”

“Well - it’s funny,” said Fatty. “I can’t understand it either.”

“It’s not much use you going to any house-agent now and asking for the keys,” said Daisy. “If no one is selling it, there won’t be any keys to get.”

“Blow!” said Fatty, upset to find his plans coming to a full stop. He thought for a minute. “Well, I’ll tell you what I could do - I could go to the biggest house-agent’s in the village, and ask about houses for sale and mention Milton House. I could see if he says anything interesting.”

“Yes - you could do that,” said Daisy. “You’d better be the one to do it, anyway. You’ve got cheek enough for anything, and you can be more grown-up than any of us. You could pretend you were asking for your mother or your aunt.”