NOTE: This spoiler sent in by SFarrier.

This story centers around a young and adventurous 16-year-old named Katy McLaughlin. Her dream is to work on her family’s ranch in modern-day Wyoming. But Katy's father wants more for her, insisting that Katy go to college. Katy finds a wild mustang, which she names Flicka, and sets out to make her a riding horse. But Flicka and Katy are more alike than she could have imagined. Like Katy, Flicka has a disdain for authority and is not about to give up her freedom without a fight.

The movie starts when Katy is expelled from school for not writing her final essay. She turned in a blank test booklet. Her father is furious because they barely make ends meet on their quarter horse breeding ranch so that they can send her to private school. He orders her to spend the summer working on the essay so he can get her back into the school.

Katy is thrown off her horse after being spooked by a mountain lion. Flicka rescues her by scaring the mountain lion away. Katy runs to tell her family about the mustang she found. Her father speaks down about the horse calling wild mustangs parasites that can ruin a breeding farm. Katy tries to capture Flicka and fails. Her father catches Flicka and saves her from going over a cliff. He forbids Katy from visiting Flicka. Of course she disobeys. She tries to make her a riding horse each night after everyone has gone to bed. She is found out and her father sells the horse to the rodeo owner for the wild horse ride.

There is a side story here about her brother. He wants to go to college on scholarship instead of working at the ranch while Katy wants to stay at the ranch instead of going to college. He finally tells his father what he really wants when they are arguing about selling Flicka.

She and her brother enter the wild horse ride so they can win the purse and she can buy Flicka back. She knows that she can ride Flicka long enough to win the race. Her parents realize she is on the field trying to ride Flicka. Her dad tries to stop her but she gets on Flicka, who is spooked by the other horses and takes off running.

Katy and Flicka ride all the way home. It is dark and raining when they finally reach the outskirts of the ranch. A mountain lion attacks and wounds Flicka, who falls to the ground. Katy’s family and the ranch hands search throughout the night for them. One of the hands finds her unconscious with a severely wounded Flicka and takes Katy home. She is sick and feverish due to exposure. Her father orders the ranch hands to shoot Flicka to put her out of her misery. They refuse and say that Katy will hear the shot. Her father decides to do it himself because he does not want the horse to suffer. A few minutes later a shot rings out. While Katy is unconscious, her father reads the notes she has written about her love of the ranch and the horse. He emails them to the school headmaster.

The next day when her fever breaks, she comes running down the stairs to find out where they put Flicka. Her mother takes her to a bandaged Flicka and her father. He says he doesn’t know how Flicka survived the mountain lion attack but she did, just like Katy did. The movie ends with the camera panning away from the entrance to the ranch where a sign has been added saying the ranch is now also a mustang rescue facility.