Dear Enemy is the sequel to Jean Webster's novel Daddy-Long-Legs. The story as presented in a series of letters written by Sallie McBride, Judy Abbott's college mate in Daddy-Long-Legs. Among the recipients of the letters are the president of the orphanage where Sallie is filling in until a new director can be installed, his wife (Judy Abbott of Daddy-Long-Legs), and the orphanage's doctor (to whom Sallie addresses her letters: "Dear Enemy"). (Summary from Wikipedia)
