Moondial by Helen Cresswell

Even before she came to Belton, Minty Cane had known that she was a witch, or something very like it. . . .

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

On night-time expeditions from the house where she’s staying, Minty stumbles upon a moondial which takes her back in time. There she finds Tom, a sickly kitchen boy, and Sarah, a girl whose family thinks she has the mark of the devil. . . .

Will Minty find her way home, or will she get stuck in the past forever. . .?