Julian whistled. “Yes — the jackdaws build in the tower, which is by the little room — and anyone going into the room would disturb them. I believe you’re right, George.”

“It’s been puzzling me awfully where Uncle Quentin could be doing his work,” said Dick. “I simply could not solve the mystery — but now I think we have!”

“I wonder how Father found his hiding-place,” said George, thoughtfully. “I still think it was mean of him not to tell me.”

“There must have been some reason,” said Dick, sensibly. “Don’t start brooding again!”

“I’m not,” said George. “I’m puzzled, that’s all. I wish we could take the boat and go over to the island at once, and explore!”

“Yes. I bet we’d find the entrance all right now,” said Dick. “Your father is sure to have left some trace of where it is — a stone a bit cleaner than the rest — or weeds scraped off — or something.”

“Do you suppose the unknown enemy on the island knows Uncle Quentin’s hiding-place?” said Anne, suddenly. “Oh, I do hope he doesn’t! He could so easily shut him in if he did.”

“Well, he hasn’t gone there to shut Uncle up — he’s gone there to steal his secret, or find it out,” said Julian. “Golly, I’m thankful he’s got Timmy. Timmy could tackle a dozen enemies.”

“Not if they had guns,” said George, in a small voice. There was a silence. It was not a nice thought to think of Timmy at the wrong end of a gun. This had happened once or twice before in their adventures, and they didn’t want to think of it happening again.

“Well, it’s no good thinking silly things like that,” said Dick, getting up. “We’ve had a jolly interesting half-hour. I think we’ve solved that mystery. But I suppose we shan’t know for certain till your father’s finished his experiment, George, and left the island — then we can go over and have a good snoop round.”

“It’s still raining,” said Anne, looking out of the window. “But it’s a bit clearer. It looks as if the sun will be out soon. Let’s go for a walk.”

“I shall go up to the coastguard’s cottage,” said George, at once. “I want to look through his telescope to see if I can just get a glimpse of Timmy.”

“Try the field-glasses,” suggested Julian. “Go up to the top of the house with them.”

“Yes, I will,” said George. “Thanks for the idea.”

She fetched the field-glasses, where they hung in the hall, and took them out of their leather case. She ran upstairs with them. But she soon came down again, looking disappointed.

“The house isn’t high enough for me to see much of the island properly. I can see the glass top of the tower easily, of course — but the telescope would show it much better. It’s more powerful. I think I’ll go up and have a squint. You don’t need to come if you don’t want to.” She put the glasses back into their case.