Darach by Hazel Hunter

To escape her stalker, an artist travels back in time.

Charlotte Walsh is so relieved to have survived a murderous attack in an alley that landing in a medieval Scottish hot spring is no big deal. But the massive highland warrior bathing there most definitely is.
Chieftain Darach MacRoss has his hands full as head of the garrison, but when Charlotte literally drops into his life his priorities change. But as he becomes her protector, a series of accidents make it clear that someone wants him dead.

When Charlotte recognizes the pattern of the attacks, she knows what she must do.