Jimmy Wakely and his pal "Cannonball" are hired by rancher and horse breeder Tom Chadwick to capture Midnight, a wild stallion that has been interfering with local herds and has a reputation as a killer. After they capture the horse, Jimmy decides to break him. At the saloon in town, Tom, meanwhile, is being systematically fleeced of his money and property in crooked poker games run by owners Monica and Brent, and their employee Lannigan. Although Jimmy succeeds in taming Midnight, Laura, Tom's daughter, tells him the horse is an outlaw and refuses to allow it on the ranch. At the saloon, Jimmy observes a poker game Tom is involved in and reveals that Lannigan has been cheating by hiding cards up his sleeve. Lannigan slugs Jimmy and a fistfight ensues, which Jimmy wins. Monica pretends to be surprised that Lannigan was cheating, throws him out and apologizes to Tom. At the ranch, Midnight becomes agitated around Laura, frightening her, but Jimmy proves to her that the horse can be very docile. Later, on the ranch racetrack, Jimmy works out Midnight in a race against Tom's fastest horse and wins, while Monica and Brent look on from a distance. However, Gentry, Tom's trainer, has no enthusiasm for Midnight and does not want to breed him with their mares. Monica bets Tom that her horse, Ace High, can beat Midnight in a race and invites him to visit her the next day to finalize the details. Meanwhile, when Gentry complains to Monica and Brent about Tom's plan to use Midnight as a stud with his thoroughbred mares, Monica suggests to him that Tom might change his mind if Midnight were to lose the race. The next day, Monica tells Tom that she will bet him $40,000 on the race, which is to take place in two days' time. The night before the race, Tom discovers Gentry and Brent doping Midnight, and Brent slugs Tom, accidentally killing him, then makes it appear that Midnight was responsible. Later, Jimmy, Cannonball and Laura find Tom's body and Midnight gone. After her father's funeral, Laura fires Jimmy and Cannonball and is advised by Monica to sell the ranch. Laura intends to track down Midnight and kill him. After she sets off alone, Jimmy and Cannonball find evidence that suggests that Midnight is not guilty, ride after Laura and arrive in time to prevent her from shooting the horse. However, the evidence is tampered with and Jimmy suspects that Gentry is involved. When Jimmy asks Monica for work, she tells him that Laura has decided to sell the ranch to her and offers him the foreman's job. Meanwhile, Brent has allowed Gentry to win a lot of money in a poker game. After Jimmy tells Gentry that he is going to round up Midnight and prove his innocence, Gentry plots to destroy the device used to incriminate the horse, unaware that Monica has ordered Brent to have him killed afterward. Jimmy and Cannonball follow Gentry and surprise him, but Monica's henchman, Gurk, shoots Gentry before he can incriminate anyone. Jimmy chases after Gurk on horseback and shoots him. With his dying breath, Gentry tells Jimmy that Brent killed Tom and that Monica wanted Midnight to lose the race. Just as Laura is about to sign over the ranch to Monica and Brent, Cannonball arrives and asks her to come with him immediately to see Gentry, who wants to confess something about her father's death. When Brent shoots what he thinks is Gentry's injured body, Jimmy surprises him, chases him and lassos him off his horse. The sheriff tells Monica that he saw Brent shoot at "Gentry," and when Jimmy returns with Brent, he arrests her and Brent. Laura apologizes to Jimmy, and before he and Cannonball move on to their next adventure, they leave Midnight with Laura.
