At the beginning of Chapter 6, David is informed that Sophie and her parents have been captured. After learning this news and having been beaten, David decides to run away from home.
This news of the Wenders capture is especially disturbing to David because when he was being beaten (in Chapter 5) he apparently revealed that the Wenders fled when Sophie's secret was discovered by Alan, the son of John Ervin, the blacksmith, a boy only a couple of years older than David.
"I couldn't help it, Sophie,' I sobbed, 'I couldn't help it." David cries from the beating as well as from his shame of betraying Sophie. And, even though David is told the next day by the inspector that his having informed on the Wenders was not the cause of their capture since they were picked up by a patrol who happened to discover them simply by chance, he decides to run away. But, when David tells his sympathetic Uncle Axel his plans, the man advises,
"I'd not do that, ...It doesn't usually work very well. Besides...where would you run to?'
Uncle Axel warns David that he will have to show his papers and his identity will be revealed, so he will just be returned to his father, and things will be worse. As a former sailor, Uncle Axel also knows what is beyond the world David knows and informs David so that he is able to convince David to remain in Waknuk, at least temporarily.