And then both he and Anne heard another sound — a faraway chug-chug-chug-chug-chug.

“It’s a motor-boat,” said Anne, listening. “Isn’t it Timmy? Someone’s having a very late trip! Can you see any ship-lights, Tim? I can’t.”

The engine of the motor-boat cut out just then, and there was complete silence except for the swish-swash-swish of the waves on the beach. Anne strained her eyes to see if she could spot any light anywhere to show where the motor-boat was. It sounded quite far out on the bay. Why had it stopped on the water? Why hadn’t it gone to the jetty?

Then she did see a light, but a very faint one, right out at the entrance of the bay, about the middle. It shone for a while, moved here and there, and then disappeared. Anne was puzzled.

“Surely that’s just about where Kirrin Island is?” she whispered to Timmy. “Is anyone there? Has the motor-boat gone there, do you suppose? Well, we’ll listen to see if it leaves again and goes away.”

But no further sound came from across the bay, and no light shone either. “Perhaps the motor-boat is behind Kirrin Island,” thought Anne, suddenly. “And then I wouldn’t be able to see any lights on it — the island would hide the boat and its lights. But what was that moving light I saw? Was it someone on the island? Oh dear, my eyes are getting so sleepy again that I can hardly keep them open. Perhaps I didn’t hear or see anything after all!”

There was no more thunder, and no lightning at all. The big black cloud began to thin out and one or two stars appeared in the gaps. Anne yawned and crawled into bed. Timmy jumped back on George’s bed and curled himself up with a little sigh.

In the morning Anne had almost forgotten her watch at the open window the night before. It was only when Joan mentioned that a big storm had burst over a town fifty miles away that Anne remembered the thunder she had heard.

“Oh!” she said, suddenly. “Yes—I heard thunder too, and I got out of bed, hoping to watch a storm. But it didn’t come. And I heard a motor-boat far out on the bay, but I couldn’t see any lights — except for a faint, moving one I thought was on Kirrin Island.”

George sat up in her chair as if she had had an electric shock. “On Kirrin Island! Whatever do you mean? Nobody’s there. Nobody’s allowed there!”

“Well — I may have been mistaken,” said Anne. “I was so very sleepy. I didn’t hear the motor-boat go away. I just went back to bed.”

“You might have waked me, if you thought you saw a light on my island,” said George. “You really might!”

“Oh, Miss Anne — it wouldn’t be kidnappers, would it!” said Joan, at once.

Julian laughed. “No, Joan. What would be the use of them going to Kirrin Island? They couldn’t do any kidnapping there, in full view of all the houses round the bay!”