Mickey Miller is a thoroughly modern 12-year-old New Yorker who has little enthusiasm for her mother's plan to take her and her little brother to start a new life Longwood, a windswept town in Ireland. Their arrival in Longwood, however, coincides with the return of the Black Knight, a legendary ruler whose appearances always mean that something evil is going to happen. Realizing that she is directly linked to the story of the Black Knight, Mickey and her new friend Sean – along with Silver, the wildest, most untamable horse in the stalls of a nearby castle – set out to redeem the knight. But first she must save a precious herd of white horses and thwart the plans of a greedy, ambitious woman – a mighty handful even for the bravest girl!