Carrie's War by Nina Bawden
Albert, Carrie and young Nick are war-time evacuees whose lives get so tangled up with the people they've come to live among that the war and their real families seem to belong to another world. Carrie and Nick are billeted in Wales with old Mr Evans, who is so mean and cold, and his timid mouse of a sister, Lou, who suddenly starts having secrets. Their friend Albert is luckier, living in Druid's Bottom with warm-hearted Hepzibah Green and the strange Mister Johnny, who can talk to animals but not to human beings. Carrie and Nick visit him there whenever they can for Hepzibah makes life exciting and enticing with her stories and delicious cooking. Gradually they begin to feel more at ease in their war-time home, but then, in trying to heal the rift between Mr Evans and his estranged sister, and save Druid's Bottom, Carrie does a terrible thing which is to haunt her for years to come. Carrie revisits Wales as an adult and tells the story to her own children.