When thirteen-year-old Samantha returns home to her family's cattle ranch in Nevada, she's nervous. She moved away two years ago to recover from a bad fall off her beloved mustang, Blackie, and she's still not sure she can get back in the saddle. She's having trouble bonding with her new horse, Ace, the other ranchers treat her like the boss's spoiled daughter, and Blackie has been missing since the day of Sam's fateful accident.

But that's just the beginning. On a moonlit night, a mustang comes to Sam. Is it Blackie grown up and gone wild--or the legendary phantom stallion? When Sam suddenly finds the fate of the horse resting in her hands, she has to be a real cowgirl, ready or not.