The situation of the story is given in the first few paragraphs. A military man, who we come to know as Captain Torres, enters the barbershop. The barber, who is narrating the tale, becomes very nervous, but tries to hide his emotions from his customer:
Hoping to conceal my emotion, I continued sharpening the razor.
The complication comes when we realise that Captain Torres has just been out hunting rebel forces. The barber confesses that he is a member of the rebel group, and therefore an enemy of Captain Torres and implacably imposed to what he stands for. Captain Torres also shows himself to be a cruel torturer of rebels, describing the torture of rebels as "A fine show" as he forced all of the villagers to go past the "mutilated" hanging bodies, which were then used for firing practice.
The central conflict that the barber faces is whether he should take advantage of the ideal opportunity and kill his enemy or whether he should do his job "honourably" and give him a good shave. Note how the barber describes the options open to him:
Murderer or hero? My destiny depends on the edge of this blade.
However, the resolution comes when the barber decides that he does not want to be a murder and just wants "lather" on his hands, and not blood. The sting in the tale at the end of the story lies in the fact that all through the silent, internal deliberation of the barber, Captain Torres has known that the barber is a rebel:
In the doorway he paused for a moment and said, "They told me that you'd kill me. I came to find out. But killing isn't easy. You can take my word for it." And he turned and walked away.