I Shall Wear Midnight - Terry Pratchett

The fourth in a series of Discworld novels starring the young witch Tiffany Aching.

As the witch of the Chalk, Tiffany Aching performs the distinctly unglamorous work of caring for the needy. But someone--or something--is inciting fear, generating dark thoughts and angry murmurs against witches. Tiffany must find the source of unrest and defeat the evil at its root. Aided by the tiny-but-tough Wee Free Men, Tiffany faces a dire challenge, for if she falls, the whole Chalk falls with her. . . .