"The Secret of Green Knowe" is a children's novel by L.M. Boston that follows the adventures of a young boy named Tolly who visits his great-grandmother's ancient house, Green Knowe. The house is filled with history and magic, and Tolly discovers that it is inhabited by the spirits of children from the past. As Tolly explores the grounds, he learns about the lives of these children, including Ping, a Chinese boy, and Bramble and Basil, siblings from the 18th century. The story weaves together themes of friendship, imagination, and the connection between past and present.