It's kids' week at the ranch, and Kirstie befriends Lacey, a loner with a natural talent for riding. Besotted with her horse, a blue roan gelding called Gunsmoke, Lacey breaks ranch rules and rides off trail alone. When she fails to return, Kirstie fears the worst; either Lacey has had a terrible accident, or she's run away - unaware that a heavy storm is brewing...