Heimweh nach der Gasse

...except with a boy as the central character.

A clean-cut young son of a working-class war widow returns a purse that a wealthy American woman has dropped in a department store, and she's so impressed that she wants to adopt him and give him a good education and cultured manners. To his mother's surprise he agrees, but he doesn't tell her it's so that she'll be free to marry the man she's been seeing and not have to worry about the man's reaction to gaining a whole family.

At first he loves his new privileged life, but soon gets upset at the way his new stepmother keeps showing him off to friends and increasingly exaggerating the story of how she saved him from a life of poverty. He also misses his real mother, who has since married her suitor. Eventually he runs away, leading to a simultaneously touching and amusing if predictable conclusion.