The lie tree Hardinge Frances

The Lie Tree is a wonderfully evocative and atmospheric novel by Frances Hardinge, award-winning author of Cuckoo Song and Fly By Night. Faith's father has been found dead under mysterious circumstances, and as she is searching through his belongings for clues she discovers a strange tree. The tree only grows healthy and bears fruit if you whisper a lie to it. The fruit of the tree, when eaten, will deliver a hidden truth to the person who consumes it. The bigger the lie, the more people who believe it, the bigger the truth that is uncovered.
The girl realizes that she is good at lying and that the tree might hold the key to her father's murder, so she begins to spread untruths far and wide across her small island community. But as her tales spiral out of control, she discovers that where lies seduce, truths shatter . . .