Mary Lennox is a troubled, sickly, and unloved 10-year-old girl born in India to selfish, wealthy British parents. When her parents die, she is sent to live with her uncle in Yorkshire, England. As Mary is exploring the periphery of her uncle's gardens, a robin draws her attention to an area of turned-over soil. Mary finds the key to a locked garden, and begins an adventure that will change her life forever.
The growth in the garden and Mary is the book's central symbol. Using the garden motif, Burnett explores the healing power inherent in living things. In a very literal sense, Mary Lennox "comes alive" as her garden does. The Secret Garden is now Burnett's most popular novel, and is considered to be a classic of English children's literature.