Charlotte lives in a big house with lots of toys but she is not happy, she wants to play with her friends and you can't have better friends than Tim and Ginger when they're bound for adventure, and trouble.

#5 in the Little Tim series:
Tim and Ginger rescue a girl on the beach, but upon recovering she can't remember her name or what happened to her -- so they call her Charlotte and she becomes part of the household. Then suddenly an elderly woman shows up. It's Charlotte's Aunt Agatha (for Charlotte's real name is, funnily enough, Charlotte) and the sight of her triggers the return of her memory -- of how she fell overboard on her aunt's yacht. It turns out Charlotte is a very rich little girl and Aunt Agatha takes her back to be one. But Charlotte misses Tim and his family -- though Aunt Agatha considers them unsuitable and wild. Charlotte's health declines and expensive doctors are called, until the only solution is to send her back, despite Aunt Agatha's disapproval. Meanwhile Tim has been horribly teased at school for missing Charlotte, even getting into a huge fight ("Tim's Last Stand"). The three children -- Tim, Ginger, and Charlotte -- are happily reunited, spending time telling (and listening to) tales of the sea.

Definite social class issues!