Darcy Heart O'Hara, a young Irish girl who neglects her chores to observe the beauties of nature and everyday life, shares "family memories" with her homesick parents and siblings after the O'Haras are forced to emigrate to America in the 1840s.
A family retells the story of the shillelagh that was whittled from a tree. During the Irish potato famine, Fergus and his family left for America. But first Fergus cut a branch from a blackthorn tree to take a piece of Ireland with him.
After being injured while racing in Ireland’s famous Foster Stakes, the Black and Alec head to the Irish coast to recuperate. While there, they are charmed by the pleasant people and intrigued by tales of the kelpie, a shape-shifting creature of myth who carries unsuspecting riders off to a watery grave. Alec meets a lonely local girl, Mora, who has found a stray pony. Alec, recognizing her love of horses, teaches her to ride. But when Mora disappears, Alec realizes that she has been carried off by the mythical kelpie. Now, Alec and the Black must race the shape-shifter, not realizing that if they lose, not only will Mora be lost forever, but so will the Black.