A boy, Jody, walks home from school one day. On the way home he catches frogs and bugs and stores them in his lunch tin. An imaginary army follows behind him. When he arrives home, his mother tells him his father wants to speak with him. His often stern father tells him that he will pay the five dollars to have their mare, Nellie, bred, if Jody will raise the colt. He is giving Jody this responsibility because the barn hand, Billy Buck, said Jody is capable. Jody is flattered and excited.

The next day, Jody takes Nellie to breed. For the next year he watches her, waiting for a sign of pregnancy. Billy Buck tells him how long it will be until the birth and what it will be like. Jody often ask him if the colt will be okay, which offends Billy, because up until recently Billy was faultless. But not too long ago a colt died under his watch. Billy promises Jody that he won’t let anything happen to the colt if he can.

Eventually, Nellie starts to show. One night Jody has a bad dream, and goes out to the barn to see her. Billy tells him to go back to bed, and that he’ll wake him if anything happens. Later that night, Billy wakes Jody, and tells him to rush out to the barn. When they get there, Billy declares that something is terribly wrong. He yells at Jody to look away, and hits Nellie in the head, killing her. Billy pulls out the healthy colt and lays it at Jody’s feet. Billy says, “There’s your colt, the way I promised."