When Jo Tiegan is given a mirror as a gift by the elderly owner of an antique shop, she is amazed to see another girl's image in the mirror instead of her own reflection. It is also quite obvious that the other girl can see her just as clearly. Jo (from the 1990's) and the girl in the mirror, Louisa (from 1919), later find that they can also travel to each other's times through the mirror - setting in motion a relentless sequence of events.