The Secret Garden by Louise May Alcott

The Secret garden (1911) tells the story of orphaned Mary Lennox who comes to live at her uncle's great house on the Yorkshire Moors and finds it full of strange secrets. The hous eis full of locked rooms and she rarely catches a glimpse of her uncle. Most frightening of all, she hears the sound of somone crying at night.  She spends her days exploring the garden and longs to find out what is beind the mysterious walled-in, locked garden. So, what happens when she finds a key?