Mary Lennox grew up in India, with an indifferent mother and busy father.  She is used to being alone, so she is angry when after the death of her parents in a cholera epidemic, she is sent to England.  Lonely and neglected, she makes friends with the brother of a servant, Dickon, and discovers an equally loney and neglected child in the house; her cousin Colin.  The three children become friends, despite their different backgrounds and work together on the secret walled garden that once had belonged to Colin's dead mother.  Mr Craven, Colin's father, has left his son to the care of servants.  Over the years, the lonely boy has become an invalid who is barely able to walk.  His energetic cousin at first repells and then coaxes him to try to grow stronger and live again, like the garden.  It all ends happily of course.  Colin becomes strong and lively, Mary finds a family as well as a garden to love and Mr Craven comes back to life.

Frances Hodgson Burnett began writing The Secret Garden in the late 1890's, after she was divorced from her husband and had returned to live in England.  The house where she lived had several walled gardens, including a rose garden, where she wrote. You can read the full text of the novel here.