Kelsie is the spirited protagonist who tries to rescue a rebellious horse named Caspar. Kelsie plans to swim this horse to Mackay's Island, a mysterious deserted island with a dark past, before the horse's owner, Hank Harefield, ships him off for auction. Along the way a violent storm puts Kelsie and Caspar in grave danger. Will they make it to shore safely? Will Hank discover and foil Kelsie's plan?