An Enemy at Green Knowe

"Tolly and his Chinese friend, Ping, spend their holiday at Green Knowe, the home of Tolly's grandmother. ... [A]n alchemist who once lived in the nine-hundred-year-old stone house, who disappeared following his confession to the local clergyman who helped him burn his mysterious books, comes alive to the boys in the person of one Melanie Powers. ..." --contemporary review by Kirkus (undated online)