“My little boy—William—is in there!” answered his mother. “He must have gone back up the steps when my back was turned.”

“Well, he’ll be all right. Don’t worry,” advised the conductor, kindly.

“I’ll get him!” offered Mr. Martin, with a laugh. “There was a little girl with some picture books in the aisle across from William,” he explained, “and I think Trouble climbed back there to get another look at the pictures. I’ll get him!”

While some passengers stuck their heads out of windows to find the cause for the sudden stopping of the train, after it had started, Mr. Martin and the conductor made their way into the car that had just been left.

But, to the surprise of the father of the Curlytops, William was not in there. The little girl and her mother, in whom the small lad had been much interested, were still looking at the picture book, but Trouble was not in sight.

“That’s queer,” murmured Mr. Martin. “Excuse me,” he spoke to the lady with the little girl, “but did you see my little boy come back into this car? He got off with us, but we missed him after we had taken stock of our bags, and I thought he had climbed back on the train again.”

“No, he didn’t come in here,” said the lady.

“That’s queer!” murmured Trouble’s father.

“Maybe he got in one of the other cars,” suggested the conductor. “Though he’d have to be pretty lively on his feet to do that.”

“Trouble is pretty quick,” said Mr. Martin.