Great question. It is clear that at the beginning of the tale the narrator is terrified of Captain Torres - he is forced to "conceal his emotion" and knows well the kind of ruthless individual he has before him, having witnessed what he has done to his fellow rebels before. And yet, it is clear that by the end of the story, both characters seemed to have formed some kind of grudging respect for the other. The narrator is faced with the dilemma of whether he should kill the Captain or not, and in the end concludes:
But I don't want to be a murderer. You came to me for a shave. And I perform my work honourably... I don't want blood on my hands. Just lather, that's all. You are an executioner and I am only a barber. Each person has his own place in the scheme of things.
The narrator therefore seems to identify that both he and Captain Torres have their own "place in the scheme of things" and that they both have different expertise. This evidence of grudging respect is seen by Captain Torres as well, for at the end of the story, in a surprising twist, he reveals that he knew the narrator was in league with the rebels, and yet he lets him live.
Therefore when we think about the relationship between the narrator and Captain Torres, we are shown a relationship that is based initially on power and fear, yet it comes to be characterised by a kind of grudging respect and realisation about the place that each occupy in the world and how hard it is to be a murderer.