"What's up?" Duane, her foot on her pedal ready to mount, paused and looked back. "My back tyre's down as flat as a pancake." "A puncture?" "'Fraid so," replied Kitty gloomily. "I'll see if I can pump it up, though." A brief examination proved the fact beyond a doubt. Kitty looked at Duane. The two had been the last to leave the farmhouse--where the cycling party had had tea--and were the only girls left behind, the others having ridden on a minute or two before Kitty's discovery. "You ride on and overtake the others," she said. "I'll mend the puncture and come on afterwards. If I scorch I might catch you up some time. Only it won't be long before it gets dark." "Oh, I'll lend a hand," said Duane good-naturedly. "I've got my lamps. Besides, Miss Carslake wouldn't like one of us to be left alone." "As to that, I'm quite capable of looking after myself," returned the Australian girl rather impatiently. "But it's good of you to stay, though, and keep me company." The two girls were accustomed to mending their own punctures. They had some difficulty at first in locating this one, but with the aid of a bucket of water borrowed from the obliging farm people, found it and patched it up. "That's done at last!" exclaimed Kitty with a sigh of relief, as she unscrewed her pump. "Now we can get on. Hallo, who on earth's this? Why," in great amazement, "it's Bertha! What on earth is she doing here?" They hailed her, and in another minute Bertha had ridden up and jumped off her bicycle. They could see that she was in a state of great agitation. "Is Erica with you?" she called out breathlessly. "Erica? No, she's with the others, I expect," answered Kitty quickly. "They went on ahead some time ago. Didn't you pass them?" "Yes. She wasn't with them. They told me she was behind with you. I wasn't sure of it, but I just said nothing and came on to find you." "But what are you doing here, Bertha?" asked Duane, for Bertha had not been one of the members of the cycling party. "As you know," Bertha answered hurriedly, "I went over to Sheerston's this afternoon. When I came back I found Erica had left this note behind for me, and I can tell you it nearly knocked me over when I read it. I borrowed a bike from one of the girls and came on as fast as I could, hoping to get here before you left." She had pulled an envelope from her pocket as she spoke, and handed it over to Duane. The head prefect read it through quickly and silently. Her face was grave when she handed it back. "Great Scott! So that's why she was so anxious to come on the cycling expedition, is it? Poor little kid! But why on earth should she choose this way in which to run away from school?"