The barber is the narrator of the story. He is a man who takes pride in his work and considers himself the best barber in town. He is brave, has a great deal of self-control, and is not a person who wants to commit violence. When Captain Torres describes his past treatment of the rebels and his plans to punish newly captured ones, the barber considers how easy it would be to kill him. But he knows that the captain would only be replaced by another cruel man, and moreover, the barber understands that he himself is a man who doesn't want blood on his hands. He is, however, willing to work with the rebels and inform on Captain Torres's group; his identity is a guarded secret among the rebels.
Captain Torres is the leader of the men who are hunting down the rebels. He is brutal, cruel, and shrewd. He comes in to get a shave specifically because he is told by someone—he doesn't specify who exactly—that the barber will murder him; he wants to get his own measure of the man. He puts away his weapons and exposes his throat to the barber as he talks about the horrible things he and his men have done to the rebels. He's cruel because he doesn't only kill the rebels—he also brutalizes them—for instance, he punishes the rebels by hanging them and then having his men do target practice on their bodies. His cruelty has made a large impression on the rebels and on the barber. Before he leaves, he lets the barber know that he came to see whether the man would kill him, and he tells him that killing is hard. This last piece of information shows that the captain may have some kind of conscience; if he didn't, killing would be easy, and he wouldn't warn the barber about it.
The rebels are working against Captain Torres's men. They've often been caught and brutalized. Though they don't appear in the action of the story, the captain uses a discussion of them and the punishments he inflicts on them to determine what actions the barber will take when pushed.