The Greengage Summer by Rumer Godden

The faded elegance of Les Oeillets, with its bullet-scarred staircase and serene garden bounded by high walls; Eliot, the charming Englishman who became the children's guardian while their mother lay ill in hospital; sophisticated Mademoiselle Zizi, hotel patronne, and Eliot's devoted lover; 16 year old Joss, the oldest Grey girl, suddenly, achingly beautiful. And the Marne river flowing silent and slow beyond them all ...They would merge together in a gold-green summer of discovery, until the fruit rotted on the trees and cold seeped into their bones ...