Senor is only a horse, a thoroughbred, and winner of many blue ribbons. On account of old age, Jim Hartwell, the ranch owner, orders Steve, an employee, to take the old horse into the foothills and shoot him. Kitty, Hartwell's daughter, loves old Senor and claims him for her personal property. Steve loves Kitty and refuses to shoot the horse. In anger, Hartwell discharges him. The ranch owner, mounting his horse, leads Senor to the foothills. He takes the bit of blue ribbon which Kitty had tied in Senor's foretop, and throws it aside. Just as he raises his revolver to shoot, he sees a Mexican creeping towards his horse in the act of stealing it. He turns his attention towards the thief, who shoots Hartwell. Steve appears, and fires at the Mexican, who in turn, shoots Steve and escapes. Steve, not seriously wounded, turns his attention to Mr. Hartwell. The Mexican makes his way afoot across the hills and comes across a party of range riders. He notifies them that Hartwell is dead and that he saw Steve shoot him. Steve is found bending over Hartwell. Mr. Hartwell is taken back to his ranch and Steve is delivered to the sheriff. Hartwell regains consciousness, but has lost all recollection of what has happened. Kitty tries in vain to make him recall the incidents of the shooting. He suddenly catches sight of Senor and immediately regains his memory and declares the innocence of Steve and the guilt of the Mexican. Kitty has learned that the sheriff and the ranchmen are about to hang Steve for the crime. She rushes from the house, mounts old Senor and is soon riding wildly to Steve's rescue. On her way, she is intercepted by the Mexican and thrown from her horse. He jumps on Senor's back and tries to make his escape in the opposite direction. She hastens on foot to stay Jim's execution and reaches there just in time to save him. Steve is released and the men hastily go in pursuit of the Mexican, whom they capture and condemn to death. Confronted with the evidence of his guilt, the bit of blue ribbon, which he had picked up when he shot Hartwell and dropped when he stopped Kitty on her way to Steve's rescue, he confesses and is sentenced to death.