The Scorpio Races by Maggie Stiefvater is a novel about two teenagers, Sean and Puck, who take part in the dangerous Scorpio Races that take place on the island of Thisby each Fall. Based on the legends of the eich uisce — the Celtic water horse — Each November, water horses emerge from the black ocean and gallop the beach beneath the cliffs of Thisby. And each November, men attempt to tame these horses in order to ride them in a thrilling and deadly race. Both Sean and Puck have their own reasons for participating in the races, but as their friendship develops, they are both forced to reconsider their priorities.
Sean watched his father die while participating in the Scorpio Races when he was only ten years old. After this, Sean vows never to be afraid as his father was, and looks forward to being able to participate in the races when he is older. Nine years later, he is preparing for his first race.
Mutt Malvern, the son of Sean’s boss, torments Sean incessantly. Though Sean does his best to ignore the taunting, he dreams of independence and a life where he doesn’t have to put up with Mutt. After a piebald mare named Skata is captured, Sean attempts to ride the horse and finds that she is much too aggressive. He warns that she will kill someone.
Puck decides to get involved when her older brother, Gabe, tells her that he is moving to the mainland and leaving Thisby. Puck decides to ride in the Scorpio Races against her brothers’ wishes. Uncomfortable with the idea of riding a capaill uisce, Puck decides to ride her island pony, Dove. She registers for the races, despite objections from the other riders who see a girl on the beach as bad luck.
The first time Sean sees Puck on the beach, he watches her from a distance just in time to see her get knocked off her mount. He tells her to keep her pony off his beach. Puck is mortified, so much so that she considers withdrawing from the races. Her resolve is reinforced when she gets a visit from Benjamin Malvern who warns her that she and her brothers are about to get evicted as no one has been making the mortgage payments since her parents died.
Meanwhile, his son Mutt continues to do everything in his power, including taking the brutal loss of a colt, to demonstrate his contempt for Sean. While they are out on the water in Malvern’s boat, Mutt lets a capaill uisce attack Fundamental, a colt and one of Sean’s charges. Sean tries desperately to save Fundamental, but fails.
After this event, Sean desperately wants to quit his job. The only thing holding him back is the thought of losing Corr, his beloved capaill stallion. On top of everything else, Sean soon learns that Mutt is planning to ride Skata in the races. Sean has previously warned Mutt of the dangers of the horse but Mutt is unconcerned over the fact that Skata might kill someone.
Before the races, all of the participants gather for a bonfire. The men object to Puck’s participation in the races, but Sean defends her, telling the others of her courage and determination and forcing them to concede. Sean is so inspired by Puck’s bravery that he decides to confront Malvern about letting him buy Corr. Malvern refuses, and Sean retreats, feeling defeated.
A heavy storm hits, causing the horses at Malvern Yard to act up. Although Sean is at odds with Malvern, he offers to help anyway, unable to bear the thought of a horse getting injured over his conflict with his boss. After the storm passes, Malvern insists that nothing has changed, still refusing to give up Corr. Puck is furious when she hears this, and insists that Corr belongs to Sean no matter what the law says. Malvern finally comes around and agrees to sell Sean the horse if he wins the race.
As Puck and Sean grow closer, yet both equally determined to win the race, their friendship becomes increasingly complicated. Puck laments the fact that she and Sean cannot both win the race. Sean and Puck end up kissing and discussing their dreams of becoming king and queen of the race and blowing away the rest of the competition.
Finally, the day of the Scorpio Races arrives. As promised, Sean waits for Puck to make her move in the race before he makes his. However, just as she is about to make her move, Malvern moves in on Puck with Skata, forcing Sean to intervene. Skata attacks Corr, knocking Sean off the horse’s back. Puck finds herself at the finish line alone, shocked to have won the race and wondering what has happened to Sean. She turns back to see his body lying on the ground, guarded by Corr.
Puck convinces Malvern to sell Corr to Sean in spite of his loss. The events of the race have left Corr badly wounded, and Sean decides it is best to release him back to the sea where he can find happiness.