Moondial

Minty is the kind of girl who notices things. Pockets of cold air on a stairway. Cries on the wind. Ghosts.

On night-time jaunts from the house where she's staying while her mother recovers from an accident, Minty stumbles upon a moondial which takes her back in time. She finds Tom, a sickly kitchen boy, and Sarah, a girl with a birthmark who is only allowed out at night because her family think she has the mark of the devil...