A Skinful of Shadows | Francis Hardinge

The spirit is wild, brutish and strong, and it may be her only defence when she is sent to live with her father's rich and powerful ancestors. There is talk of civil war, and they need people like her to protect their dark and terrible family secret.

But as she plans her escape and heads out into a country torn apart by war, Makepeace must decide which is worse: possession - or death.